An affix is a morpheme‏‎ that is attached to a root‏‎ (or stem) of a word‎ to form another word.

For example, take the word reason and add two affixes:
un + reason + able
Prefixes and suffixes are common types of affixes.

A prefix is an affix which is placed before a root.
un + kind = unkind
re + act = react
mis +…