What is a derivational affix?

Definition
	A derivational affix is an affix by means of which one word is formed (derived) from another. The derived word is often of a different word class from the original.

Discussion
	In contrast to an inflectional affix, a derivational affix
	is not part of an obligatory set of affixes generally occurs closer to the root generally is more meaningful, and is more likely to result in a form that has a somewhat idiosyncratic meaning.

Examples (English)
	Joyful Joyfulness Stapler

Kinds
	Here are some kinds of derivational affixes:
	What is a productive affix? What is an unproductive affix?

Generic
	A derivational affix is a kind of
	What is an affix? (Linguistics)