thorough knowledge or mastery of a thing, subject, etc.

the state of being familiar; friendly relationship; close acquaintance; intimacy.

an absence of ceremony and formality; informality.

freedom of behavior justified only by the closest relationship; undue intimacy.

Often, familiarities. an instance of such freedom, as in action or speech.

a sexual liberty or impropriety.

noun

aloofness , cool , distance , frigidity , reserve , unfriendliness , ignorance , unfamiliarity , strangeness

noun

acquaintance , acquaintanceship , boldness , closeness , ease , fellowship , forwardness , freedom , freshness , friendship , informality , intimacy , liberty , naturalness , openness , presumption , sociability , unceremoniousness , awareness , cognition , comprehension , experience , feel , grasp , knowledge , sense , understanding , chumminess , companionship , comradeship , assumption , audaciousness , audacity , brashness , brazenness , cheek , cheekiness , chutzpah , discourtesy , disrespect , effrontery , face , gall , impertinence , impudency , incivility , insolence , nerve , nerviness , overconfidence , pertness , presumptuousness , pushiness , rudeness , sassiness , sauciness , confidentiality , conversance , topos , unconstraint , unreserve