Affix

(Affixes are also known as a "Bound Morphemes".)

Affixes are building blocks of words (morphemes) that cannot exist as independent words. They have meaning, but they are only understood when joined to a root word.

For example, the prefix un- does not have a clear meaning. However, the un- prefix in unforgetable is understood to change the meaning of forgetable to mean the opposite of forgetable.

Position
Affixes can be classified by their position in a word.

Function
Affixes can also be classified by their function, or what they change, in a word.

Other things to know about affixes:

 * Affixes do not belong to word classes. i.e. a prefix can not be classified as a noun.