As a Noun:
1. A person who is sitting down, a seated person.
2. A piece of furniture for one person to sit on, with a back and four legs. English = chair.
3. An object you can sit on, for example a chair. English = seat.
As a Verb or Adjective:
1. To be on something, such as a chair, so that your weight is supported by your buttocks rather than your feet, and the upper part of your body is upright. English = sit, sit on.