sit down
phr. v..phr. v.. To move your body from a standing position to a sitting position, for example on a chair or the floor.
phr. v.. An intransitive phrasal verb meaning to lower oneself into a seated position. It can also function transitively and separably (e.g., sit someone down).
Please sit down and wait here.
After a long walk, it felt good to sit down and rest my feet.
The negotiators agreed to sit down together, hoping to finally resolve the long-standing dispute through direct dialogue.
Often used as a polite command or invitation, especially with 'please'.
Contrast 'sit down' (the action of sitting) with 'be sitting' (the state of being seated) using simple commands and descriptions.
He sat down the chair.He sat down on the chair.The phrase 'sit down' describes the action; you still need a preposition like 'on' or 'in' to say where you sat.