diff --git a/async/async.d.ts b/async/async.d.ts
index a1e1f12b9..ec92487fc 100644
--- a/async/async.d.ts
+++ b/async/async.d.ts
@@ -3,65 +3,65 @@
 // Definitions by: Boris Yankov <https://github.com/borisyankov/>
 // Definitions: https://github.com/borisyankov/DefinitelyTyped
 
-
-interface AsyncCallback<T> { (err: string, results: T[]): any; }
-interface AsyncIterator<T> { (item: T, callback: AsyncCallback<T>): void; }
-interface AsyncMemoIterator<T> { (memo: T, item: T, callback: AsyncCallback<T>): void; }
+interface AsyncMultipleResultsCallback<T> { (err: string, results: T[]): any; }
+interface AsyncSingleResultCallback<T> { (err: string, result: T): any; }
+interface AsyncIterator<T> { (item: T, callback: AsyncMultipleResultsCallback<T>): void; }
+interface AsyncMemoIterator<T> { (memo: T, item: T, callback: AsyncSingleResultCallback<T>): void; }
 interface AsyncWorker<T> { (task: T, callback: Function): void; }
 
 interface AsyncQueue<T> {
     length(): number;
     concurrency: number;
-    push(task: T, callback: AsyncCallback<T>): void;
-    saturated: AsyncCallback<T>;
-    empty: AsyncCallback<T>;
-    drain: AsyncCallback<T>;
+    push(task: T, callback: AsyncMultipleResultsCallback<T>): void;
+    saturated: AsyncMultipleResultsCallback<T>;
+    empty: AsyncMultipleResultsCallback<T>;
+    drain: AsyncMultipleResultsCallback<T>;
 }
 
 interface Async {
 
     // Collections
-    forEach<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>): void;
-    forEachSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>): void;
-    forEachLimit<T>(arr: T[], limit: number, iterator: AsyncIterator<T>, callback: AsyncCallback<T>): void;
-    map<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    mapSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    filter<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    select<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    filterSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    selectSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    reject<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    rejectSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    reduce<T>(arr: T[], memo: T, iterator: AsyncMemoIterator<T>, callback: AsyncCallback<T>);
-    inject<T>(arr: T[], memo: T, iterator: AsyncMemoIterator<T>, callback: AsyncCallback<T>);
-    foldl<T>(arr: T[], memo: T, iterator: AsyncMemoIterator<T>, callback: AsyncCallback<T>);
-    reduceRight<T>(arr: T[], memo: T, iterator: AsyncMemoIterator<T>, callback: AsyncCallback<T>);
-    foldr<T>(arr: T[], memo: T, iterator: AsyncMemoIterator<T>, callback: AsyncCallback<T>);
-    detect<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    detectSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    sortBy<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    some<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    any<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    every<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    all<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    concat<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
-    concatSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncCallback<T>);
+    forEach<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>): void;
+    forEachSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>): void;
+    forEachLimit<T>(arr: T[], limit: number, iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>): void;
+    map<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    mapSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    filter<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    select<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    filterSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    selectSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    reject<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    rejectSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    reduce<T>(arr: T[], memo: T, iterator: AsyncMemoIterator<T>, callback: AsyncSingleResultCallback<T>);
+    inject<T>(arr: T[], memo: T, iterator: AsyncMemoIterator<T>, callback: AsyncSingleResultCallback<T>);
+    foldl<T>(arr: T[], memo: T, iterator: AsyncMemoIterator<T>, callback: AsyncSingleResultCallback<T>);
+    reduceRight<T>(arr: T[], memo: T, iterator: AsyncMemoIterator<T>, callback: AsyncSingleResultCallback<T>);
+    foldr<T, U>(arr: T[], memo: T, iterator: AsyncMemoIterator<T>, callback: AsyncSingleResultCallback<T>);
+    detect<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    detectSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    sortBy<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    some<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    any<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    every<T>(arr: T[], iterator: AsyncIterator<T>, callback: (result: boolean) => any);
+    all<T>(arr: T[], iterator: AsyncIterator<T>, callback: (result: boolean) => any);
+    concat<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
+    concatSeries<T>(arr: T[], iterator: AsyncIterator<T>, callback: AsyncMultipleResultsCallback<T>);
 
     // Control Flow
-    series<T>(tasks: T[], callback?: AsyncCallback<T>): void;
-    series<T>(tasks: T, callback?: AsyncCallback<T>): void;
-    parallel<T>(tasks: T[], callback?: AsyncCallback<T>): void;
-    parallel<T>(tasks: T, callback?: AsyncCallback<T>): void;
-    whilst(test: Function, fn: Function, callback: AsyncCallback): void; // TODO: generify
-    until(test: Function, fn: Function, callback: AsyncCallback): void; // TODO: generify
-    waterfall<T>(tasks: T[], callback?: AsyncCallback<T>): void;
-    waterfall<T>(tasks: T, callback?: AsyncCallback<T>): void;
+    series<T>(tasks: T[], callback?: AsyncMultipleResultsCallback<T>): void;
+    series<T>(tasks: T, callback?: AsyncMultipleResultsCallback<T>): void;
+    parallel<T>(tasks: T[], callback?: AsyncMultipleResultsCallback<T>): void;
+    parallel<T>(tasks: T, callback?: AsyncMultipleResultsCallback<T>): void;
+    whilst(test: Function, fn: Function, callback: Function): void;
+    until(test: Function, fn: Function, callback: Function): void;
+    waterfall<T>(tasks: T[], callback?: AsyncMultipleResultsCallback<T>): void;
+    waterfall<T>(tasks: T, callback?: AsyncMultipleResultsCallback<T>): void;
     queue<T>(worker: AsyncWorker<T>, concurrency: number): AsyncQueue<T>;
-    //auto(tasks: any[], callback?: AsyncCallback<T>): void;
-    auto<T>(tasks: T, callback?: AsyncCallback<T>): void;
+    //auto(tasks: any[], callback?: AsyncMultipleResultsCallback<T>): void;
+    auto<T>(tasks: T, callback?: AsyncMultipleResultsCallback<T>): void;
     iterator(tasks): Function;
     apply(fn: Function, ...arguments: any[]): void;
-    nextTick<T>(callback: AsyncCallback<T>): void;
+    nextTick<T>(callback: AsyncMultipleResultsCallback<T>): void;
 
     // Utils
     memoize(fn: Function, hasher?: Function): Function;