乐 (lè) is a bound form meaning 'happiness' or 'joy', appearing as the main meaning component in common words like 快乐 (happy), 欢乐 (joyful), 乐趣 (fun), and 乐观 (optimistic). Do not confuse it with the reading yuè, which means 'music' (e.g., 音乐). As a surname, 乐 is typically read yuè, but the lè reading also exists in some dialect usages. This entry covers only the lè (happy/joyful) reading.