S: (n) eon, aeon (the longest division of geological time)
S: (n) period, geological period (a unit of geological time during which a system of rocks formed) "ganoid fishes swarmed during the earlier geological periods"
S: (n) time (the continuum of experience in which events pass from the future through the present to the past) "he waited for along time"; "it took some time before he got an answer"; "time flies like an arrow"