grandad vs grandpa

grandad and grandpa both are nouns.

Word	Noun	Adjective	Verb	Adverb
grandad	Yes	No	No	No
grandpa	Yes	No	No	No

As nouns, grandad and grandpa are synonyms defined as:

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

grandad (noun)	grandpa (noun)
the father of your father or mother	the father of your father or mother