granddaddy vs grandad

granddaddy and grandad both are nouns.

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

As nouns, granddaddy and grandad are synonyms defined as:

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

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