diff --git a/src/lib/es2015.collection.d.ts b/src/lib/es2015.collection.d.ts
index 43129531845e4..a01b21dded868 100644
--- a/src/lib/es2015.collection.d.ts
+++ b/src/lib/es2015.collection.d.ts
@@ -94,7 +94,7 @@ interface Set<T> {
      */
     has(value: T): boolean;
     /**
-     * @returns the number of (unique) elements in Set.
+     * @returns the number of (unique) elements in the Set.
      */
     readonly size: number;
 }
diff --git a/src/lib/es2015.symbol.d.ts b/src/lib/es2015.symbol.d.ts
index 9ede0239fafbe..32bb690d3189c 100644
--- a/src/lib/es2015.symbol.d.ts
+++ b/src/lib/es2015.symbol.d.ts
@@ -19,7 +19,7 @@ interface SymbolConstructor {
 
     /**
      * Returns a key from the global symbol registry matching the given Symbol if found.
-     * Otherwise, returns a undefined.
+     * Otherwise, returns undefined.
      * @param sym Symbol to find the key for.
      */
     keyFor(sym: symbol): string | undefined;