A(n) is a behavior or mental act that a person repeats over and over in an effort to reduce anxiety.

Compulsion

Explanation:

Compulsion is usually defined as a type of behavior or a kind of mental act that a person does or feels like doing it continuously, over and over again, in response to a particular mania. A person does these types of mental acts in order to minimize the level of anxiety. This type of illness occurs when a person reaches such a point in terms of anxiety that it forces him/her to do such things. It affects both the physical and mental health of a person.

Community, also called biological community, in biology, an interacting group of various species in a common location. For example, a forest of trees and undergrowth plants, inhabited by animals and rooted in soil containing bacteria and fungi, constitutes a biological community.