請關燈。

Please turn off the light.

Turn off the light, please.

Source: Tatoeba

Sentence Composition

=1 請 qǐng
  1. to ask
  2. to invite
  3. please (do sth)
  4. to treat (to a meal etc)
  5. to request
=1 請 qīng only used in 請室／请室 (qīngshì)
2 關燈 guāndēng to turn off a light