Concern is a versatile English word with multiple meanings:
1. As a noun: a matter of interest or importance to someone ("This is my main concern")
2. As a noun: a feeling of worry ("She expressed concern about the situation")
3. As a verb: to relate to or affect ("This matter concerns all of us")
4. As a verb: to cause worry ("His health concerns me")
5. In business: a company or enterprise ("a multinational concern")