From WordNet (r) 3.0 (2006):
dawn
n 1: the first light of day; "we got up before dawn"; "they
talked until morning" [syn: dawn, dawning, morning,
aurora, first light, daybreak, break of day, break
of the day, dayspring, sunrise, sunup, cockcrow]
[ant: sundown, sunset]
2: the earliest period; "the dawn of civilization"; "the morning
of the world" [syn: dawn, morning]
3: an opening time period; "it was the dawn of the Roman Empire"
v 1: become clear or enter one's consciousness or emotions; "It
dawned on him that she had betrayed him"; "she was
penetrated with sorrow" [syn: click, get through,
dawn, come home, get across, sink in, penetrate,
fall into place]
2: appear or develop; "The age of computers had dawned"
3: become light; "It started to dawn, and we had to get up"