granddad vs granddaddy

granddad and granddaddy both are nouns.

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

As nouns, granddad and granddaddy are synonyms defined as:

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

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