postfix vs affix

postfix and affix both are nouns.

Word	Noun	Adjective	Verb	Adverb
postfix	Yes	No	No	No
affix	Yes	No	Yes	No

As nouns, affix is a hypernym of postfix; that is, affix is a word with a broader meaning than postfix:

postfix: an affix that is added at the end of the word
affix: a linguistic element added to a word to produce an inflected or derived form

Other hypernyms of postfix include ending, termination.

postfix (noun)	affix (noun)
an affix that is added at the end of the word	a linguistic element added to a word to produce an inflected or derived form

postfix (verb)	affix (verb)
	stick or fasten to
	add to the very end
	attach or become attached to a stem word