As a Noun:
1. The part of something that normally faces towards the ground. English = underside.
As a Verb or Adjective:
1. To be located directly below or beneath something. English = (be) under, (be) underneath.
2. To move so that you are located directly below or beneath something. English = go under.
3. To be located under the surface of the ground. English = (be) underground.
4. To be in the power or control of a particular person or government. English = (be) under.