grandmother vs grandma

grandmother and grandma both are nouns.

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

As nouns, grandmother and grandma are synonyms defined as:

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

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