granddad vs gramps

granddad and gramps both are nouns.

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

As nouns, granddad and gramps are synonyms defined as:

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

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