What's the difference between i.e. and e.g.?
early 15c., "harmony, agreement," from Medieval Latin correspondentia, from correspondentem (nominative correspondens), present participle of correspondere (see correspond). Sense of "communication by letters" is first attested 1640s.
correspondence cor·re·spon·dence (kôr'ĭ-spŏn'dəns)
A relationship between corresponding points on each retina such that stimulation produces a single image.