well known from long or close association

their faces will be familiar to many of you

a familiar voice

in close friendship; intimate

she had not realized they were on such familiar terms

a demon supposedly attending and obeying a witch, often said to assume the form of an animal

her familiars were her two little griffons that nested in her skirts

a close friend or associate

(in the Roman Catholic Church) a person rendering certain services in a pope's or bishop's household