你必须在天黑前回来。

You must come back before it gets dark.

Source: Tatoeba

Sentence Composition

=1 你 nǐ you (informal, as opposed to courteous 您 nín)
=1 你 nǐ you (Note: In Taiwan, 妳 is used to address females, but in mainland China, it is not commonly used. Instead, 你 is used to address both males and females.)
2 必须 bìxū
  1. to have to
  2. must
  3. compulsory
  4. necessarily
3 在 zài
  1. to exist; to be alive
  2. (of sb or sth) to be (located) at
  3. (used before a verb to indicate an action in progress)
4 天黑 tiānhēi
  1. to get dark
  2. dusk
5 前 qián
  1. front
  2. forward
  3. ahead
  4. first
  5. top (followed by a number)
  6. future
  7. ago
  8. before
  9. BC (e.g. 前293年)
  10. former
  11. formerly
=6 回来 huílai to return; to come back
=6 回来 huílái
  1. (to come or bring) back (used after a verb to indicate direction towards the speaker)
  2. back (used after a verb to indicate direction towards the speaker)
  3. to return; to come back; to be back