diff --git a/docs/modules/Array.ts.md b/docs/modules/Array.ts.md
index 035a25075..e96f5452a 100644
--- a/docs/modules/Array.ts.md
+++ b/docs/modules/Array.ts.md
@@ -112,6 +112,7 @@ Added in v2.0.0
   - [chainRecBreadthFirst](#chainrecbreadthfirst)
   - [chainRecDepthFirst](#chainrecdepthfirst)
   - [chainWithIndex](#chainwithindex)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [traverseWithIndex](#traversewithindex)
 - [traversing](#traversing)
@@ -1701,15 +1702,7 @@ Added in v2.0.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to
-determine the next computation.
-
-In other words it takes a function `f` that produces an array from a single element of
-the base type `A` and returns a new function which applies `f` to each element of the
-input array (like [`map`](#map)) and, instead of returning an array of arrays, concatenates the
-results into a single array (like [`flatten`](#flatten)).
-
-This is the `chain` component of the array `Monad`.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1717,17 +1710,6 @@ This is the `chain` component of the array `Monad`.
 export declare const chain: <A, B>(f: (a: A) => B[]) => (ma: A[]) => B[]
 ```
 
-**Example**
-
-```ts
-import { chain, map, replicate } from 'fp-ts/Array'
-import { pipe } from 'fp-ts/function'
-
-const f = (n: number) => replicate(n, `${n}`)
-assert.deepStrictEqual(pipe([1, 2, 3], map(f)), [['1'], ['2', '2'], ['3', '3', '3']])
-assert.deepStrictEqual(pipe([1, 2, 3], chain(f)), ['1', '2', '2', '3', '3', '3'])
-```
-
 Added in v2.0.0
 
 ## chainFirst
@@ -1807,6 +1789,35 @@ assert.deepStrictEqual(pipe(['a', 'b', 'c'], chainWithIndex(f)), ['a0', 'a0', 'b
 
 Added in v2.7.0
 
+## flatMap
+
+Composes computations in sequence, using the return value of one computation to
+determine the next computation.
+
+In other words it takes a function `f` that produces an array from a single element of
+the base type `A` and returns a new function which applies `f` to each element of the
+input array (like [`map`](#map)) and, instead of returning an array of arrays, concatenates the
+results into a single array (like [`flatten`](#flatten)).
+
+**Signature**
+
+```ts
+export declare const flatMap: { <A, B>(f: (a: A) => B[]): (ma: A[]) => B[]; <A, B>(ma: A[], f: (a: A) => B[]): B[] }
+```
+
+**Example**
+
+```ts
+import { flatMap, map, replicate } from 'fp-ts/Array'
+import { pipe } from 'fp-ts/function'
+
+const f = (n: number) => replicate(n, `${n}`)
+assert.deepStrictEqual(pipe([1, 2, 3], map(f)), [['1'], ['2', '2'], ['3', '3', '3']])
+assert.deepStrictEqual(pipe([1, 2, 3], flatMap(f)), ['1', '2', '2', '3', '3', '3'])
+```
+
+Added in v2.14.0
+
 ## flatten
 
 Takes an array of arrays of `A` and flattens them into an array of `A`
diff --git a/docs/modules/Either.ts.md b/docs/modules/Either.ts.md
index 1e39965aa..28faebae4 100644
--- a/docs/modules/Either.ts.md
+++ b/docs/modules/Either.ts.md
@@ -158,6 +158,7 @@ Added in v2.0.0
   - [chainOptionK](#chainoptionk)
   - [chainOptionKW](#chainoptionkw)
   - [chainW](#chainw)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [flattenW](#flattenw)
 - [traversing](#traversing)
@@ -1327,7 +1328,7 @@ Added in v2.0.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1408,9 +1409,7 @@ Added in v2.13.2
 
 ## chainW
 
-Less strict version of [`chain`](#chain).
-
-The `W` suffix (short for **W**idening) means that the error types will be merged.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1418,30 +1417,20 @@ The `W` suffix (short for **W**idening) means that the error types will be merge
 export declare const chainW: <E2, A, B>(f: (a: A) => Either<E2, B>) => <E1>(ma: Either<E1, A>) => Either<E2 | E1, B>
 ```
 
-**Example**
-
-```ts
-import * as E from 'fp-ts/Either'
-import { pipe } from 'fp-ts/function'
+Added in v2.6.0
 
-const e1: E.Either<string, number> = E.right(1)
-const e2: E.Either<number, number> = E.right(2)
+## flatMap
 
-export const result1 = pipe(
-  // @ts-expect-error
-  e1,
-  E.chain(() => e2)
-)
+**Signature**
 
-// merged error types -----v-------------v
-// const result2: E.Either<string | number, number>
-export const result2 = pipe(
-  e1, // no error
-  E.chainW(() => e2)
-)
+```ts
+export declare const flatMap: {
+  <A, E2, B>(f: (a: A) => Either<E2, B>): <E1>(ma: Either<E1, A>) => Either<E2 | E1, B>
+  <E1, A, E2, B>(ma: Either<E1, A>, f: (a: A) => Either<E2, B>): Either<E1 | E2, B>
+}
 ```
 
-Added in v2.6.0
+Added in v2.14.0
 
 ## flatten
 
diff --git a/docs/modules/IO.ts.md b/docs/modules/IO.ts.md
index 0c3be2fd4..818e93e81 100644
--- a/docs/modules/IO.ts.md
+++ b/docs/modules/IO.ts.md
@@ -50,6 +50,7 @@ Added in v2.0.0
 - [sequencing](#sequencing)
   - [chain](#chain)
   - [chainFirst](#chainfirst)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
 - [traversing](#traversing)
   - [sequenceArray](#sequencearray)
@@ -281,7 +282,7 @@ Added in v2.0.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -304,6 +305,19 @@ export declare const chainFirst: <A, B>(f: (a: A) => IO<B>) => (first: IO<A>) =>
 
 Added in v2.0.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, B>(f: (a: A) => IO<B>): (ma: IO<A>) => IO<B>
+  <A, B>(ma: IO<A>, f: (a: A) => IO<B>): IO<B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/IOEither.ts.md b/docs/modules/IOEither.ts.md
index 63df300d1..7dd6ff5ac 100644
--- a/docs/modules/IOEither.ts.md
+++ b/docs/modules/IOEither.ts.md
@@ -104,6 +104,7 @@ Added in v2.0.0
   - [chainOptionK](#chainoptionk)
   - [chainOptionKW](#chainoptionkw)
   - [chainW](#chainw)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [flattenW](#flattenw)
 - [traversing](#traversing)
@@ -917,7 +918,7 @@ Added in v2.10.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1056,9 +1057,7 @@ Added in v2.13.2
 
 ## chainW
 
-Less strict version of [`chain`](#chain).
-
-The `W` suffix (short for **W**idening) means that the error types will be merged.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1070,6 +1069,19 @@ export declare const chainW: <E2, A, B>(
 
 Added in v2.6.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, E2, B>(f: (a: A) => IOEither<E2, B>): <E1>(ma: IOEither<E1, A>) => IOEither<E2 | E1, B>
+  <E1, A, E2, B>(ma: IOEither<E1, A>, f: (a: A) => IOEither<E2, B>): IOEither<E1 | E2, B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/IOOption.ts.md b/docs/modules/IOOption.ts.md
index 715e2dd5b..9f6919a4f 100644
--- a/docs/modules/IOOption.ts.md
+++ b/docs/modules/IOOption.ts.md
@@ -89,6 +89,7 @@ Added in v2.12.0
   - [chainIOK](#chainiok)
   - [chainNullableK](#chainnullablek)
   - [chainOptionK](#chainoptionk)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
 - [traversing](#traversing)
   - [traverseReadonlyArrayWithIndex](#traversereadonlyarraywithindex)
@@ -714,6 +715,8 @@ Added in v2.12.0
 
 ## chain
 
+Alias of `flatMap`.
+
 **Signature**
 
 ```ts
@@ -797,6 +800,19 @@ export declare const chainOptionK: <A, B>(f: (a: A) => O.Option<B>) => (ma: IOOp
 
 Added in v2.12.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, B>(f: (a: A) => IOOption<B>): (ma: IOOption<A>) => IOOption<B>
+  <A, B>(ma: IOOption<A>, f: (a: A) => IOOption<B>): IOOption<B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/Identity.ts.md b/docs/modules/Identity.ts.md
index 39ad19813..145fc4b5a 100644
--- a/docs/modules/Identity.ts.md
+++ b/docs/modules/Identity.ts.md
@@ -51,6 +51,7 @@ Added in v2.0.0
 - [sequencing](#sequencing)
   - [chain](#chain)
   - [chainFirst](#chainfirst)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
 - [traversing](#traversing)
   - [sequence](#sequence)
@@ -388,7 +389,7 @@ Added in v2.0.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -411,6 +412,16 @@ export declare const chainFirst: <A, B>(f: (a: A) => B) => (first: A) => A
 
 Added in v2.0.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: { <A, B>(f: (a: A) => B): (ma: A) => B; <A, B>(ma: A, f: (a: A) => B): B }
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/NonEmptyArray.ts.md b/docs/modules/NonEmptyArray.ts.md
index b29b90334..5e26d31af 100644
--- a/docs/modules/NonEmptyArray.ts.md
+++ b/docs/modules/NonEmptyArray.ts.md
@@ -77,6 +77,7 @@ Added in v2.0.0
   - [chain](#chain)
   - [chainFirst](#chainfirst)
   - [chainWithIndex](#chainwithindex)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [traverseWithIndex](#traversewithindex)
 - [traversing](#traversing)
@@ -686,7 +687,7 @@ Added in v2.11.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -694,21 +695,6 @@ Composes computations in sequence, using the return value of one computation to
 export declare const chain: <A, B>(f: (a: A) => NonEmptyArray<B>) => (ma: NonEmptyArray<A>) => NonEmptyArray<B>
 ```
 
-**Example**
-
-```ts
-import * as NEA from 'fp-ts/NonEmptyArray'
-import { pipe } from 'fp-ts/function'
-
-assert.deepStrictEqual(
-  pipe(
-    [1, 2, 3],
-    NEA.chain((n) => [`a${n}`, `b${n}`])
-  ),
-  ['a1', 'b1', 'a2', 'b2', 'a3', 'b3']
-)
-```
-
 Added in v2.0.0
 
 ## chainFirst
@@ -736,6 +722,34 @@ export declare const chainWithIndex: <A, B>(
 
 Added in v2.10.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, B>(f: (a: A) => NonEmptyArray<B>): (ma: NonEmptyArray<A>) => NonEmptyArray<B>
+  <A, B>(ma: NonEmptyArray<A>, f: (a: A) => NonEmptyArray<B>): NonEmptyArray<B>
+}
+```
+
+**Example**
+
+```ts
+import * as NEA from 'fp-ts/NonEmptyArray'
+import { pipe } from 'fp-ts/function'
+
+assert.deepStrictEqual(
+  pipe(
+    [1, 2, 3],
+    NEA.flatMap((n) => [`a${n}`, `b${n}`])
+  ),
+  ['a1', 'b1', 'a2', 'b2', 'a3', 'b3']
+)
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/Option.ts.md b/docs/modules/Option.ts.md
index 0d3a7dd7c..51e21758d 100644
--- a/docs/modules/Option.ts.md
+++ b/docs/modules/Option.ts.md
@@ -157,6 +157,7 @@ Added in v2.0.0
   - [chainFirst](#chainfirst)
   - [chainFirstEitherK](#chainfirsteitherk)
   - [chainNullableK](#chainnullablek)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
 - [traversing](#traversing)
   - [sequence](#sequence)
@@ -1244,7 +1245,7 @@ Added in v2.0.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1342,6 +1343,19 @@ assert.deepStrictEqual(
 
 Added in v2.9.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, B>(f: (a: A) => Option<B>): (ma: Option<A>) => Option<B>
+  <A, B>(ma: Option<A>, f: (a: A) => Option<B>): Option<B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/Reader.ts.md b/docs/modules/Reader.ts.md
index c1ce7ffa7..ad9ba365b 100644
--- a/docs/modules/Reader.ts.md
+++ b/docs/modules/Reader.ts.md
@@ -90,6 +90,7 @@ Added in v2.0.0
   - [chainFirst](#chainfirst)
   - [chainFirstW](#chainfirstw)
   - [chainW](#chainw)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [flattenW](#flattenw)
 - [traversing](#traversing)
@@ -433,7 +434,7 @@ Added in v2.0.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -474,9 +475,7 @@ Added in v2.11.0
 
 ## chainW
 
-Less strict version of [`chain`](#chain).
-
-The `W` suffix (short for **W**idening) means that the environment types will be merged.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -486,6 +485,19 @@ export declare const chainW: <R2, A, B>(f: (a: A) => Reader<R2, B>) => <R1>(ma:
 
 Added in v2.6.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, R2, B>(f: (a: A) => Reader<R2, B>): <R1>(ma: Reader<R1, A>) => Reader<R1 & R2, B>
+  <R1, A, R2, B>(ma: Reader<R1, A>, f: (a: A) => Reader<R2, B>): Reader<R1 & R2, B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/ReaderEither.ts.md b/docs/modules/ReaderEither.ts.md
index 883340d63..06d71761d 100644
--- a/docs/modules/ReaderEither.ts.md
+++ b/docs/modules/ReaderEither.ts.md
@@ -98,6 +98,7 @@ Added in v2.0.0
   - [chainReaderK](#chainreaderk)
   - [chainReaderKW](#chainreaderkw)
   - [chainW](#chainw)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [flattenW](#flattenw)
 - [traversing](#traversing)
@@ -923,7 +924,7 @@ Added in v2.10.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1108,9 +1109,7 @@ Added in v2.11.0
 
 ## chainW
 
-Less strict version of [`chain`](#chain).
-
-The `W` suffix (short for **W**idening) means that the environment types and the error types will be merged.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1122,6 +1121,25 @@ export declare const chainW: <R2, E2, A, B>(
 
 Added in v2.6.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, R2, E2, B>(f: (a: A) => ReaderEither<R2, E2, B>): <R1, E1>(
+    ma: ReaderEither<R1, E1, A>
+  ) => ReaderEither<R1 & R2, E2 | E1, B>
+  <R1, E1, A, R2, E2, B>(ma: ReaderEither<R1, E1, A>, f: (a: A) => ReaderEither<R2, E2, B>): ReaderEither<
+    R1 & R2,
+    E1 | E2,
+    B
+  >
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/ReaderIO.ts.md b/docs/modules/ReaderIO.ts.md
index c346a78e0..a950bb079 100644
--- a/docs/modules/ReaderIO.ts.md
+++ b/docs/modules/ReaderIO.ts.md
@@ -57,6 +57,7 @@ Added in v2.13.0
   - [chainReaderK](#chainreaderk)
   - [chainReaderKW](#chainreaderkw)
   - [chainW](#chainw)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [flattenW](#flattenw)
 - [traversing](#traversing)
@@ -403,7 +404,7 @@ Added in v2.13.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -516,9 +517,7 @@ Added in v2.13.0
 
 ## chainW
 
-Less strict version of [`chain`](#chain).
-
-The `W` suffix (short for **W**idening) means that the environment types will be merged.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -530,6 +529,19 @@ export declare const chainW: <A, R2, B>(
 
 Added in v2.13.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, R2, B>(f: (a: A) => ReaderIO<R2, B>): <R1>(ma: ReaderIO<R1, A>) => ReaderIO<R1 & R2, B>
+  <R1, A, R2, B>(ma: ReaderIO<R1, A>, f: (a: A) => ReaderIO<R2, B>): ReaderIO<R1 & R2, B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/ReaderTask.ts.md b/docs/modules/ReaderTask.ts.md
index 48c0eccfe..8aae0c254 100644
--- a/docs/modules/ReaderTask.ts.md
+++ b/docs/modules/ReaderTask.ts.md
@@ -72,6 +72,7 @@ Added in v2.3.0
   - [chainReaderKW](#chainreaderkw)
   - [chainTaskK](#chaintaskk)
   - [chainW](#chainw)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [flattenW](#flattenw)
 - [traversing](#traversing)
@@ -534,7 +535,7 @@ Added in v2.3.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -723,9 +724,7 @@ Added in v2.4.0
 
 ## chainW
 
-Less strict version of [`chain`](#chain).
-
-The `W` suffix (short for **W**idening) means that the environment types will be merged.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -737,6 +736,19 @@ export declare const chainW: <R2, A, B>(
 
 Added in v2.6.7
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, R2, B>(f: (a: A) => ReaderTask<R2, B>): <R1>(ma: ReaderTask<R1, A>) => ReaderTask<R1 & R2, B>
+  <R1, A, R2, B>(ma: ReaderTask<R1, A>, f: (a: A) => ReaderTask<R2, B>): ReaderTask<R1 & R2, B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/ReaderTaskEither.ts.md b/docs/modules/ReaderTaskEither.ts.md
index 26295269b..abbabc84c 100644
--- a/docs/modules/ReaderTaskEither.ts.md
+++ b/docs/modules/ReaderTaskEither.ts.md
@@ -150,6 +150,7 @@ Added in v2.0.0
   - [chainTaskEitherKW](#chaintaskeitherkw)
   - [chainTaskK](#chaintaskk)
   - [chainW](#chainw)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [flattenW](#flattenw)
 - [traversing](#traversing)
@@ -1317,7 +1318,7 @@ Added in v2.10.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1812,9 +1813,7 @@ Added in v2.10.0
 
 ## chainW
 
-Less strict version of [`chain`](#chain).
-
-The `W` suffix (short for **W**idening) means that the environment types and the error types will be merged.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1826,6 +1825,25 @@ export declare const chainW: <R2, E2, A, B>(
 
 Added in v2.6.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, R2, E2, B>(f: (a: A) => ReaderTaskEither<R2, E2, B>): <R1, E1>(
+    ma: ReaderTaskEither<R1, E1, A>
+  ) => ReaderTaskEither<R1 & R2, E2 | E1, B>
+  <R1, E1, A, R2, E2, B>(ma: ReaderTaskEither<R1, E1, A>, f: (a: A) => ReaderTaskEither<R2, E2, B>): ReaderTaskEither<
+    R1 & R2,
+    E1 | E2,
+    B
+  >
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/ReadonlyArray.ts.md b/docs/modules/ReadonlyArray.ts.md
index dcc45e67f..bd7fc74f1 100644
--- a/docs/modules/ReadonlyArray.ts.md
+++ b/docs/modules/ReadonlyArray.ts.md
@@ -110,6 +110,7 @@ Added in v2.5.0
   - [chainRecBreadthFirst](#chainrecbreadthfirst)
   - [chainRecDepthFirst](#chainrecdepthfirst)
   - [chainWithIndex](#chainwithindex)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [traverseWithIndex](#traversewithindex)
 - [traversing](#traversing)
@@ -1249,7 +1250,7 @@ Added in v2.5.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1257,28 +1258,6 @@ Composes computations in sequence, using the return value of one computation to
 export declare const chain: <A, B>(f: (a: A) => readonly B[]) => (ma: readonly A[]) => readonly B[]
 ```
 
-**Example**
-
-```ts
-import * as RA from 'fp-ts/ReadonlyArray'
-import { pipe } from 'fp-ts/function'
-
-assert.deepStrictEqual(
-  pipe(
-    [1, 2, 3],
-    RA.chain((n) => [`a${n}`, `b${n}`])
-  ),
-  ['a1', 'b1', 'a2', 'b2', 'a3', 'b3']
-)
-assert.deepStrictEqual(
-  pipe(
-    [1, 2, 3],
-    RA.chain(() => [])
-  ),
-  []
-)
-```
-
 Added in v2.5.0
 
 ## chainFirst
@@ -1346,6 +1325,43 @@ export declare const chainWithIndex: <A, B>(f: (i: number, a: A) => readonly B[]
 
 Added in v2.7.0
 
+## flatMap
+
+Composes computations in sequence, using the return value of one computation to determine the next computation.
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, B>(f: (a: A) => readonly B[]): (ma: readonly A[]) => readonly B[]
+  <A, B>(ma: readonly A[], f: (a: A) => readonly B[]): readonly B[]
+}
+```
+
+**Example**
+
+```ts
+import * as RA from 'fp-ts/ReadonlyArray'
+import { pipe } from 'fp-ts/function'
+
+assert.deepStrictEqual(
+  pipe(
+    [1, 2, 3],
+    RA.flatMap((n) => [`a${n}`, `b${n}`])
+  ),
+  ['a1', 'b1', 'a2', 'b2', 'a3', 'b3']
+)
+assert.deepStrictEqual(
+  pipe(
+    [1, 2, 3],
+    RA.flatMap(() => [])
+  ),
+  []
+)
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/ReadonlyNonEmptyArray.ts.md b/docs/modules/ReadonlyNonEmptyArray.ts.md
index e5f772828..be65557be 100644
--- a/docs/modules/ReadonlyNonEmptyArray.ts.md
+++ b/docs/modules/ReadonlyNonEmptyArray.ts.md
@@ -79,6 +79,7 @@ Added in v2.5.0
   - [chain](#chain)
   - [chainFirst](#chainfirst)
   - [chainWithIndex](#chainwithindex)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [traverseWithIndex](#traversewithindex)
 - [traversing](#traversing)
@@ -722,7 +723,7 @@ Added in v2.11.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -732,21 +733,6 @@ export declare const chain: <A, B>(
 ) => (ma: ReadonlyNonEmptyArray<A>) => ReadonlyNonEmptyArray<B>
 ```
 
-**Example**
-
-```ts
-import * as RNEA from 'fp-ts/ReadonlyNonEmptyArray'
-import { pipe } from 'fp-ts/function'
-
-assert.deepStrictEqual(
-  pipe(
-    [1, 2, 3],
-    RNEA.chain((n) => [`a${n}`, `b${n}`])
-  ),
-  ['a1', 'b1', 'a2', 'b2', 'a3', 'b3']
-)
-```
-
 Added in v2.5.0
 
 ## chainFirst
@@ -791,6 +777,34 @@ export declare const chainWithIndex: <A, B>(
 
 Added in v2.10.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, B>(f: (a: A) => ReadonlyNonEmptyArray<B>): (ma: ReadonlyNonEmptyArray<A>) => ReadonlyNonEmptyArray<B>
+  <A, B>(ma: ReadonlyNonEmptyArray<A>, f: (a: A) => ReadonlyNonEmptyArray<B>): ReadonlyNonEmptyArray<B>
+}
+```
+
+**Example**
+
+```ts
+import * as RNEA from 'fp-ts/ReadonlyNonEmptyArray'
+import { pipe } from 'fp-ts/function'
+
+assert.deepStrictEqual(
+  pipe(
+    [1, 2, 3],
+    RNEA.flatMap((n) => [`a${n}`, `b${n}`])
+  ),
+  ['a1', 'b1', 'a2', 'b2', 'a3', 'b3']
+)
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/State.ts.md b/docs/modules/State.ts.md
index 04245f95a..6d78b4358 100644
--- a/docs/modules/State.ts.md
+++ b/docs/modules/State.ts.md
@@ -34,6 +34,7 @@ Added in v2.0.0
 - [sequencing](#sequencing)
   - [chain](#chain)
   - [chainFirst](#chainfirst)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
 - [traversing](#traversing)
   - [sequenceArray](#sequencearray)
@@ -236,12 +237,12 @@ Added in v2.0.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
 ```ts
-export declare const chain: <E, A, B>(f: (a: A) => State<E, B>) => (ma: State<E, A>) => State<E, B>
+export declare const chain: <S, A, B>(f: (a: A) => State<S, B>) => (ma: State<S, A>) => State<S, B>
 ```
 
 Added in v2.0.0
@@ -259,6 +260,19 @@ export declare const chainFirst: <S, A, B>(f: (a: A) => State<S, B>) => (ma: Sta
 
 Added in v2.0.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, S, B>(f: (a: A) => State<S, B>): (ma: State<S, A>) => State<S, B>
+  <S, A, B>(ma: State<S, A>, f: (a: A) => State<S, B>): State<S, B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/StateReaderTaskEither.ts.md b/docs/modules/StateReaderTaskEither.ts.md
index d635e3e87..073c75ce5 100644
--- a/docs/modules/StateReaderTaskEither.ts.md
+++ b/docs/modules/StateReaderTaskEither.ts.md
@@ -112,6 +112,7 @@ Added in v2.0.0
   - [chainTaskEitherKW](#chaintaskeitherkw)
   - [chainTaskK](#chaintaskk)
   - [chainW](#chainw)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [flattenW](#flattenw)
 - [traversing](#traversing)
@@ -934,7 +935,7 @@ Added in v2.0.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1263,9 +1264,7 @@ Added in v2.10.0
 
 ## chainW
 
-Less strict version of [`chain`](#chain).
-
-The `W` suffix (short for **W**idening) means that the environment types and the error types will be merged.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1277,6 +1276,24 @@ export declare const chainW: <S, R2, E2, A, B>(
 
 Added in v2.6.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, S, R2, E2, B>(f: (a: A) => StateReaderTaskEither<S, R2, E2, B>): <R1, E1>(
+    ma: StateReaderTaskEither<S, R1, E1, A>
+  ) => StateReaderTaskEither<S, R1 & R2, E2 | E1, B>
+  <S, R1, E1, A, R2, E2, B>(
+    ma: StateReaderTaskEither<S, R1, E1, A>,
+    f: (a: A) => StateReaderTaskEither<S, R2, E2, B>
+  ): StateReaderTaskEither<S, R1 & R2, E1 | E2, B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/Task.ts.md b/docs/modules/Task.ts.md
index ef1d2e915..863ee4fd1 100644
--- a/docs/modules/Task.ts.md
+++ b/docs/modules/Task.ts.md
@@ -57,6 +57,7 @@ Added in v2.0.0
   - [chainFirst](#chainfirst)
   - [chainFirstIOK](#chainfirstiok)
   - [chainIOK](#chainiok)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
 - [traversing](#traversing)
   - [sequenceArray](#sequencearray)
@@ -387,7 +388,7 @@ Added in v2.0.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -430,6 +431,19 @@ export declare const chainIOK: <A, B>(f: (a: A) => IO<B>) => (first: Task<A>) =>
 
 Added in v2.4.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, B>(f: (a: A) => Task<B>): (ma: Task<A>) => Task<B>
+  <A, B>(ma: Task<A>, f: (a: A) => Task<B>): Task<B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/TaskEither.ts.md b/docs/modules/TaskEither.ts.md
index adc800252..958f9ebe2 100644
--- a/docs/modules/TaskEither.ts.md
+++ b/docs/modules/TaskEither.ts.md
@@ -127,6 +127,7 @@ Added in v2.0.0
   - [chainTaskOptionK](#chaintaskoptionk)
   - [chainTaskOptionKW](#chaintaskoptionkw)
   - [chainW](#chainw)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
   - [flattenW](#flattenw)
 - [traversing](#traversing)
@@ -1268,7 +1269,7 @@ Added in v2.10.0
 
 ## chain
 
-Composes computations in sequence, using the return value of one computation to determine the next computation.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1497,9 +1498,7 @@ Added in v2.12.3
 
 ## chainW
 
-Less strict version of [`chain`](#chain).
-
-The `W` suffix (short for **W**idening) means that the error types will be merged.
+Alias of `flatMap`.
 
 **Signature**
 
@@ -1511,6 +1510,19 @@ export declare const chainW: <E2, A, B>(
 
 Added in v2.6.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, E2, B>(f: (a: A) => TaskEither<E2, B>): <E1>(ma: TaskEither<E1, A>) => TaskEither<E2 | E1, B>
+  <E1, A, E2, B>(ma: TaskEither<E1, A>, f: (a: A) => TaskEither<E2, B>): TaskEither<E1 | E2, B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/docs/modules/TaskOption.ts.md b/docs/modules/TaskOption.ts.md
index ebc76bfbc..9633d8a74 100644
--- a/docs/modules/TaskOption.ts.md
+++ b/docs/modules/TaskOption.ts.md
@@ -84,7 +84,6 @@ Added in v2.10.0
   - [matchEW](#matchew)
   - [matchW](#matchw)
 - [sequencing](#sequencing)
-  - [chain](#chain)
   - [chainEitherK](#chaineitherk)
   - [chainFirst](#chainfirst)
   - [chainFirstEitherK](#chainfirsteitherk)
@@ -94,6 +93,7 @@ Added in v2.10.0
   - [chainNullableK](#chainnullablek)
   - [chainOptionK](#chainoptionk)
   - [chainTaskK](#chaintaskk)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
 - [traversing](#traversing)
   - [sequenceArray](#sequencearray)
@@ -114,6 +114,7 @@ Added in v2.10.0
   - [ap](#ap)
   - [apFirst](#apfirst)
   - [apSecond](#apsecond)
+  - [chain](#chain)
   - [zero](#zero)
 
 ---
@@ -826,16 +827,6 @@ Added in v2.10.0
 
 # sequencing
 
-## chain
-
-**Signature**
-
-```ts
-export declare const chain: <A, B>(f: (a: A) => TaskOption<B>) => (ma: TaskOption<A>) => TaskOption<B>
-```
-
-Added in v2.10.0
-
 ## chainEitherK
 
 **Signature**
@@ -931,6 +922,19 @@ export declare const chainTaskK: <A, B>(f: (a: A) => T.Task<B>) => (first: TaskO
 
 Added in v2.10.0
 
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, B>(f: (a: A) => TaskOption<B>): (ma: TaskOption<A>) => TaskOption<B>
+  <A, B>(ma: TaskOption<A>, f: (a: A) => TaskOption<B>): TaskOption<B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
@@ -1145,6 +1149,18 @@ export declare const apSecond: <B>(second: TaskOption<B>) => <A>(first: TaskOpti
 
 Added in v2.10.0
 
+## chain
+
+Alias of `flatMap`.
+
+**Signature**
+
+```ts
+export declare const chain: <A, B>(f: (a: A) => TaskOption<B>) => (ma: TaskOption<A>) => TaskOption<B>
+```
+
+Added in v2.10.0
+
 ## zero
 
 **Signature**
diff --git a/docs/modules/Tree.ts.md b/docs/modules/Tree.ts.md
index 413e11e99..7d4acf04b 100644
--- a/docs/modules/Tree.ts.md
+++ b/docs/modules/Tree.ts.md
@@ -20,8 +20,6 @@ Added in v2.0.0
 
 - [Extract](#extract)
   - [extract](#extract)
-- [Monad](#monad)
-  - [chain](#chain)
 - [constructors](#constructors)
   - [make](#make)
   - [of](#of)
@@ -47,7 +45,7 @@ Added in v2.0.0
   - [Comonad](#comonad)
   - [Foldable](#foldable)
   - [Functor](#functor)
-  - [Monad](#monad-1)
+  - [Monad](#monad)
   - [Pointed](#pointed)
   - [Traversable](#traversable)
   - [getEq](#geteq)
@@ -59,6 +57,8 @@ Added in v2.0.0
   - [Forest (type alias)](#forest-type-alias)
   - [Tree (interface)](#tree-interface)
 - [sequencing](#sequencing)
+  - [chain](#chain)
+  - [flatMap](#flatmap)
   - [flatten](#flatten)
 - [traversing](#traversing)
   - [sequence](#sequence)
@@ -94,20 +94,6 @@ export declare const extract: <A>(wa: Tree<A>) => A
 
 Added in v2.6.2
 
-# Monad
-
-## chain
-
-Composes computations in sequence, using the return value of one computation to determine the next computation.
-
-**Signature**
-
-```ts
-export declare const chain: <A, B>(f: (a: A) => Tree<B>) => (ma: Tree<A>) => Tree<B>
-```
-
-Added in v2.0.0
-
 # constructors
 
 ## make
@@ -512,6 +498,31 @@ Added in v2.0.0
 
 # sequencing
 
+## chain
+
+Alias of `flatMap`.
+
+**Signature**
+
+```ts
+export declare const chain: <A, B>(f: (a: A) => Tree<B>) => (ma: Tree<A>) => Tree<B>
+```
+
+Added in v2.0.0
+
+## flatMap
+
+**Signature**
+
+```ts
+export declare const flatMap: {
+  <A, B>(f: (a: A) => Tree<B>): (ma: Tree<A>) => Tree<B>
+  <A, B>(ma: Tree<A>, f: (a: A) => Tree<B>): Tree<B>
+}
+```
+
+Added in v2.14.0
+
 ## flatten
 
 **Signature**
diff --git a/src/Array.ts b/src/Array.ts
index 669bd5961..a2aa073fe 100644
--- a/src/Array.ts
+++ b/src/Array.ts
@@ -1586,7 +1586,7 @@ export const ap: <A>(fa: Array<A>) => <B>(fab: Array<(a: A) => B>) => Array<B> =
 export const flatMap: {
   <A, B>(f: (a: A) => Array<B>): (ma: Array<A>) => Array<B>
   <A, B>(ma: Array<A>, f: (a: A) => Array<B>): Array<B>
-} = dual(
+} = /*#__PURE__*/ dual(
   2,
   <A, B>(ma: Array<A>, f: (a: A) => Array<B>): Array<B> =>
     pipe(
diff --git a/src/IO.ts b/src/IO.ts
index b733e18c8..1c127d10b 100644
--- a/src/IO.ts
+++ b/src/IO.ts
@@ -78,7 +78,7 @@ export const of: <A>(a: A) => IO<A> = constant
 export const flatMap: {
   <A, B>(f: (a: A) => IO<B>): (ma: IO<A>) => IO<B>
   <A, B>(ma: IO<A>, f: (a: A) => IO<B>): IO<B>
-} = dual(
+} = /*#__PURE__*/ dual(
   2,
   <A, B>(ma: IO<A>, f: (a: A) => IO<B>): IO<B> =>
     () =>
diff --git a/src/IOOption.ts b/src/IOOption.ts
index 6884c35b5..2c21441ac 100644
--- a/src/IOOption.ts
+++ b/src/IOOption.ts
@@ -245,7 +245,7 @@ export const of: <A>(a: A) => IOOption<A> = some
 export const flatMap: {
   <A, B>(f: (a: A) => IOOption<B>): (ma: IOOption<A>) => IOOption<B>
   <A, B>(ma: IOOption<A>, f: (a: A) => IOOption<B>): IOOption<B>
-} = dual(2, OT.flatMap(I.Monad))
+} = /*#__PURE__*/ dual(2, OT.flatMap(I.Monad))
 
 /**
  * Alias of `flatMap`.
diff --git a/src/Identity.ts b/src/Identity.ts
index ee5c88d4d..9734ae22e 100644
--- a/src/Identity.ts
+++ b/src/Identity.ts
@@ -78,7 +78,7 @@ export const of: <A>(a: A) => Identity<A> = id
 export const flatMap: {
   <A, B>(f: (a: A) => Identity<B>): (ma: Identity<A>) => Identity<B>
   <A, B>(ma: Identity<A>, f: (a: A) => Identity<B>): Identity<B>
-} = dual(2, <A, B>(ma: Identity<A>, f: (a: A) => Identity<B>): Identity<B> => f(ma))
+} = /*#__PURE__*/ dual(2, <A, B>(ma: Identity<A>, f: (a: A) => Identity<B>): Identity<B> => f(ma))
 
 /**
  * Alias of `flatMap`.
diff --git a/src/Option.ts b/src/Option.ts
index 4ccabaf3a..8b285cc85 100644
--- a/src/Option.ts
+++ b/src/Option.ts
@@ -394,7 +394,7 @@ export const Applicative: Applicative1<URI> = {
 export const flatMap: {
   <A, B>(f: (a: A) => Option<B>): (ma: Option<A>) => Option<B>
   <A, B>(ma: Option<A>, f: (a: A) => Option<B>): Option<B>
-} = dual(2, <A, B>(ma: Option<A>, f: (a: A) => Option<B>): Option<B> => (isNone(ma) ? none : f(ma.value)))
+} = /*#__PURE__*/ dual(2, <A, B>(ma: Option<A>, f: (a: A) => Option<B>): Option<B> => (isNone(ma) ? none : f(ma.value)))
 
 /**
  * Alias of `flatMap`.
diff --git a/src/ReadonlyArray.ts b/src/ReadonlyArray.ts
index d397c67ad..a5b7312c1 100644
--- a/src/ReadonlyArray.ts
+++ b/src/ReadonlyArray.ts
@@ -1511,7 +1511,7 @@ export const ap: <A>(fa: ReadonlyArray<A>) => <B>(fab: ReadonlyArray<(a: A) => B
 export const flatMap: {
   <A, B>(f: (a: A) => ReadonlyArray<B>): (ma: ReadonlyArray<A>) => ReadonlyArray<B>
   <A, B>(ma: ReadonlyArray<A>, f: (a: A) => ReadonlyArray<B>): ReadonlyArray<B>
-} = dual(
+} = /*#__PURE__*/ dual(
   2,
   <A, B>(ma: ReadonlyArray<A>, f: (a: A) => ReadonlyArray<B>): ReadonlyArray<B> =>
     pipe(
diff --git a/src/State.ts b/src/State.ts
index f55ba96ad..8715434cc 100644
--- a/src/State.ts
+++ b/src/State.ts
@@ -100,7 +100,7 @@ export const of: <S, A>(a: A) => State<S, A> = (a) => (s) => [a, s]
 export const flatMap: {
   <A, S, B>(f: (a: A) => State<S, B>): (ma: State<S, A>) => State<S, B>
   <S, A, B>(ma: State<S, A>, f: (a: A) => State<S, B>): State<S, B>
-} = dual(
+} = /*#__PURE__*/ dual(
   2,
   <S, A, B>(ma: State<S, A>, f: (a: A) => State<S, B>): State<S, B> =>
     (s1) => {
diff --git a/src/Task.ts b/src/Task.ts
index 0c548a7c5..73a4699fd 100644
--- a/src/Task.ts
+++ b/src/Task.ts
@@ -132,7 +132,7 @@ export const of: <A>(a: A) => Task<A> = (a) => () => Promise.resolve(a)
 export const flatMap: {
   <A, B>(f: (a: A) => Task<B>): (ma: Task<A>) => Task<B>
   <A, B>(ma: Task<A>, f: (a: A) => Task<B>): Task<B>
-} = dual(
+} = /*#__PURE__*/ dual(
   2,
   <A, B>(ma: Task<A>, f: (a: A) => Task<B>): Task<B> =>
     () =>
diff --git a/src/TaskOption.ts b/src/TaskOption.ts
index 38ca0d6e3..e1a059afe 100644
--- a/src/TaskOption.ts
+++ b/src/TaskOption.ts
@@ -287,7 +287,7 @@ export const of: <A>(a: A) => TaskOption<A> = some
 export const flatMap: {
   <A, B>(f: (a: A) => TaskOption<B>): (ma: TaskOption<A>) => TaskOption<B>
   <A, B>(ma: TaskOption<A>, f: (a: A) => TaskOption<B>): TaskOption<B>
-} = dual(2, OT.flatMap(T.Monad))
+} = /*#__PURE__*/ dual(2, OT.flatMap(T.Monad))
 
 /**
  * Alias of `flatMap`.