index finger vs forefinger

index finger and forefinger both are nouns.

Word	Noun	Adjective	Verb	Adverb
index finger	Yes	No	No	No
forefinger	Yes	No	No	No

As nouns, index finger and forefinger are synonyms defined as:

Other synonyms of index finger include index.

index finger (noun)	forefinger (noun)
the finger next to the thumb	the finger next to the thumb