WordWeb Online

1. Personal knowledge or information about someone or something
   - acquaintance, conversance, conversancy
    
2. Usualness by virtue of being familiar or well known
    
3. Close or warm friendship
   "the absence of fences created a mysterious familiarity in which no one knew privacy"
   - intimacy, closeness
    
4. A casual manner
   - casualness
    
5. An act of undue intimacy
   - impropriety, indecorum, liberty

Derived forms: familiarities

See also: familiar, unfamiliar

Type of: friendliness, informality, information, misbehavior [US], misbehaviour [Brit, Cdn], misdeed, usualness

Antonym: unfamiliarity