grandmother vs grannie

grandmother and grannie both are nouns.

Word	Noun	Adjective	Verb	Adverb
grandmother	Yes	No	No	No
grannie	Yes	No	No	No

As nouns, grandmother and grannie are synonyms defined as:

Other synonyms of grandmother include gran, grandma, granny, nan, nanna.

grandmother (noun)	grannie (noun)
the mother of your father or mother	the mother of your father or mother