Morphological derivation

Morphological derivation, in linguistics, is the process of forming a new word from an existing word, often by adding a prefix or suffix, such as un- or -ness. For example, unhappy and happiness derive from the root word happy.

It is differentiated from inflection, which is the modification of a word to form different grammatical categories without changing its core meaning: determines, determining, and determined are from the root determine.