Wordnet 3.0
NOUN (1)
1. 
 the first light of day; 
- Example: "we got up before dawn"- Example: "they talked until morning"[syn: dawn, dawning, morning, aurora, first light, daybreak, break of day, break of the day, dayspring, sunrise, sunup, cockcrow]
WordNet (r) 3.0 (2006):
break of the day
    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]