break of the day vs dayspring

break of the day and dayspring both are nouns.

Word	Noun	Adjective	Verb	Adverb
break of the day	Yes	No	No	No
dayspring	Yes	No	No	No

As nouns, break of the day and dayspring are synonyms defined as:

Other synonyms of break of the day include aurora, break of day, cockcrow, dawn, dawning, daybreak, first light, morning, sunrise, sunup.

break of the day (noun)	dayspring (noun)
the first light of day	the first light of day