modal particle, verb, punctuation, noun, particle, adjective, pronoun, adverb, measure word, numeral, directional, suffix, place word · question particle for "yes-no" questions

你是学生吗？

noun, modal particle, punctuation · used in the transcription of morphine (吗啡 mǎ​fēi)

药瓶上贴着醒目的标签，提示里面含有吗啡等特殊成分。

verb, modal particle · (coll.) what?

你干吗呢？