The process of creating a new word out of one or more old words, either by adding a prefix or suffix or by compounding. See also: Introduction to Etymology: Word Histories.
Etymology:
From the Latin, "to draw off"Examples and Observations:
- "Morphology may be divided into derivation--rules that form a new word out of old words, like duckfeathers and unkissable--and inflection--rules that modify a word to fit its role in a sentence, what language teachers call conjugation and declension."
(Steven Pinker, Words and Rules: The Ingredients of Language, Basic Books, 1999) - "Derivational morphology studies the principles governing the construction of new words, without reference to the specific grammatical role a word might play in a sentence. In the formation of drinkable from drink, or disinfect from infect, for example, we see the formation of new words, each with its own grammatical properties."
(David Crystal, How Language Works, Overlook Press, 2005) - "Derivational prefixes do not normally alter the word class of the base word; that is, a prefix is added to a noun to form a new noun with a different meaning:
- patient: outpatient
- group: subgroup
- trial: retrial
- adjective--dark: darkness
- verb--agree: agreement
- noun--friend: friendship"

