diff --git a/src/prelude/array.ts b/src/prelude/array.ts
index 00f0dc3445..21d18a0af4 100644
--- a/src/prelude/array.ts
+++ b/src/prelude/array.ts
@@ -59,7 +59,7 @@ export function maximum(xs: number[]): number {
 
 /**
  * Splits an array based on the equivalence relation.
- * The concatenation of the result equals to the argument.
+ * The concatenation of the result is equal to the argument.
  */
 export function groupBy<T>(f: (x: T, y: T) => boolean, xs: T[]): T[][] {
 	const groups = [] as T[][];
@@ -75,7 +75,7 @@ export function groupBy<T>(f: (x: T, y: T) => boolean, xs: T[]): T[][] {
 
 /**
  * Splits an array based on the equivalence relation induced by the function.
- * The concatenation of the result equals to the argument.
+ * The concatenation of the result is equal to the argument.
  */
 export function groupOn<T, S>(f: (x: T) => S, xs: T[]): T[][] {
 	return groupBy((a, b) => f(a) === f(b), xs);