Derivational morphology is a process where one word is changed into another. The process takes a word stem like ‘national’ and adds a prefix, suffix or infix to make a new word such as ‘international’ or ‘nationality.’ The word fragments added to the stem word are called morphemes, hence morphology. There are many common morphemes in English. Such changes in derivational morphology are used to convert nouns, adjectives and verbs into one another.
Using an existing word to make a new word is called derivation. The term occurs because the meaning of the new word derivates from and away from the original meaning. It is separate from inflection, which adds additional letters, not morphemes, to a word to change its grammatical function. In this sense, changing ‘national’ to ‘nationalize’ is derivation, but turning ‘nationalize’ into ‘nationalizing’ or ‘nationalized’ is inflection and not derivation.
There are many derivational morphology combinations such as turning verbs into adjectives or nouns. Adjectives can be converted into adverbs, nouns, verbs and other adjectives. Nouns can be converted into verbs and adjectives. It is possible for each class to be converted into another word in the same class like ‘red’ and ‘reddish.’ The ability to convert one class of word into another class of word is a sign of the flexibility of English.
The term for converting an adjective or verb to a noun is called nominalization. This is a key part of derivational morphology. The adjective ‘national’ can become the verb ‘nationality.’ The verb ‘nationalize,’ itself a derivational morphology of ‘national,’ can be converted into ‘nationalization,’ a noun.
An adjective, during derivational morphology, becomes an adverb when ‘-ly’ is added to the stem word. This changes ‘ready’ into ‘readily’ and ‘slow’ into ‘slowly.’ Adjectives such as ‘slow’ can also become nouns during nominalization by adding suffixes such as ‘-ness’ to create ‘slowness.’ Adjectives such as ‘red’ can become verbs as well like ‘redden.’ Adjectives are one of the most flexible classes of word in derivational morphology.
Suffixes, prefixes and infixes perform a number of functions. The morphemes used to create such appendages to stem words rarely function as words by themselves. Some, such as ‘pro’ and ‘anti,’ became standalone words, but developed out of morphemes. Some affixes perform the same function as one another and some are preferred for some words, but not for others. For example, English has ‘atheist,’ but not ‘non-theist,’ and it has ‘polytheist,’ but not ‘multi-theist.’