gramps vs grandfather

gramps and grandfather both are nouns.

Word	Noun	Adjective	Verb	Adverb
gramps	Yes	No	No	No
grandfather	Yes	No	No	No

As nouns, gramps and grandfather are synonyms defined as:

Other synonyms of gramps include grandad, granddad, granddaddy, grandpa.

gramps (noun)	grandfather (noun)
the father of your father or mother	the father of your father or mother