ABCs vs ABC's

ABCs and ABC's both are nouns.

Word	Noun	Adjective	Verb	Adverb
ABCs	Yes	No	No	No
ABC's	Yes	No	No	No

As nouns, ABCs and ABC's are synonyms defined as:

ABCs and ABC's: a character set that includes letters and is used to write a language

Other synonyms of ABCs include ABC, alphabet.

ABCs (noun)	ABC's (noun)
a character set that includes letters and is used to write a language	a character set that includes letters and is used to write a language