么 (ma) — (question particle, informal) same as 吗, used to mark yes-no questions at the end of a sentence

吗 is the standard question particle; 么 is a casual, informal variant — sound the same (ma) and interchangeable in speech, but rarely seen in writing. Use 吗 unless you want a colloquial tone.

Most characters — around four in five — are built this way: one part hints at the meaning, the other at the pronunciation.

This origin belongs to the traditional form 麼; 么 is its simplified writing.

The traditional form 麼 pairs 麻, which gives the sound, with 幺, which means small/tiny; the simplified 么 is a later shorthand.