lunch period vs lunchtime

lunch period and lunchtime both are nouns.

Word	Noun	Adjective	Verb	Adverb
lunch period	Yes	No	No	No
lunchtime	Yes	No	No	No

As nouns, lunch period and lunchtime are synonyms defined as:

lunch period and lunchtime: the customary or habitual hour for eating lunch

lunch period (noun)	lunchtime (noun)
the customary or habitual hour for eating lunch	the customary or habitual hour for eating lunch