Index - U
| Unbox | CorePrelude, BasicPrelude |
| uncons | BasicPrelude |
| uncurry | CorePrelude, BasicPrelude |
| undefined | CorePrelude, BasicPrelude |
| unfoldr | BasicPrelude |
| uninterruptibleMask | CorePrelude, BasicPrelude |
| uninterruptibleMask_ | CorePrelude, BasicPrelude |
| union | BasicPrelude |
| unionBy | BasicPrelude |
| unless | BasicPrelude |
| unlines | BasicPrelude |
| until | CorePrelude, BasicPrelude |
| unwords | BasicPrelude |
| unzip | BasicPrelude |
| unzip3 | BasicPrelude |
| unzip4 | BasicPrelude |
| unzip5 | BasicPrelude |
| unzip6 | BasicPrelude |
| unzip7 | BasicPrelude |
| userError | CorePrelude, BasicPrelude |
| userErrorType | CorePrelude, BasicPrelude |
| UVector | CorePrelude, BasicPrelude |