别
bié
Negative commands with "bie"
别 is "don't" — the direct, spoken prohibition.
别 + Verb
How it works
别走 (don't go), 别说话 (be quiet). It's short and immediate, which is why it dominates in speech.
别 and 不要 are interchangeable in most contexts; 别 is punchier, 不要 slightly more formal.
Adding 了 gives "stop doing it": 别哭了 — stop crying.
Examples
bié zǒu
别走。
Don't go.
bié dān xīn
别担心。
Don't worry.
shàng kè de shí hou bié shuō huà
上课的时候别说话。
Don't talk during class.