n (senseid|en|noun_discourse)(context|now|_|literary) familiar | Familiar discourse; free interchange of thoughts or views; conversation; chat.
n (logic) Of a proposition or theorem of the form: given that "If A is true, then B is true", then "If B is true, then A is true." equivalently: given that "All Xs are Ys", then "All Ys are Xs".