grandad vs granddaddy

grandad and granddaddy both are nouns.

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

As nouns, grandad and granddaddy are synonyms defined as:

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

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