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.
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.