Bullying is the use of force, threat, or coercion to abuse, intimidate, or aggressively others. The behavior is often repeated and habitual. One essential prerequisite is the perception, by the bully or by others, of an imbalance of social or physical power, which distinguishes bullying from conflict. Behaviors used to assert such domination can include verbal harassment or threat, physical assault or coercion, and such acts may be directed repeatedly towards particular targets. Rationalizations for such behavior sometimes include differences of social class, race, religion, gender, sexual orientation, appearance, behavior, body language, personality, reputation, lineage, strength, size or ability. If bullying is done by a group, it is called mobbing.