Inflection is the process of adding an “affix” to a word or changing it in some other way according to the rules of the grammar of a language. Inflectional morphology studies the way in which words vary in order to express grammatical contrasts in sentences such singular/ plural or present/ past tense. Boy and boys, for example, are two forms of the same word; the choice between them, singular or plural, is a matter of grammar. This is the business of inflectional morphology.
Derivation is the formation of new words by adding “affixes” to other words or morphemes. Derivational morphology studies the principles governing the construction of new words. In the formation of “eatable” from “eat”, or “disagree” from “agree”, for example, we see the formation of different words, with their own grammatical properties.
Both inflectional and derivational morphemes are suffixes. They are bound morphemes following a root. Inflection and derivation are therefore, the sub-categories of suffixes. But they differ from each other.
(1) In inflection “suffix” is affixed to a root. For example, in “agreed” and “agrees,” “d” and “s” are suffixes and do not allow any further affixation of a suffix. Such suffixes which we do not allow further affixation are called inflections or inflectional suffixes. The suffixes which may be followed by other suffixes are called derivational suffixes. For example, “ment” “able” are derivational suffixes in “agreement” and “agreeable” because both can be followed by other suffixes and can, for instance, become “agreements” and “agreeableness” after the addition of the suffixes “s” and “ness” to agree+ment and agree+able respectively. Here
(2) We have to remember that prefixes are always derivational. For instance, in the words; disobey, impossible, etc “dis” and “im” are prefixes. Since “dis” and “im” help to construct new words “obey” and “possible” they are derivational.
(3) Inflectional suffixes are “terminal”(ending) and their termination never changes the class (parts of speech) of the root, for example in “sweeter” and “sweetest”, the termination of –“er” by “est” does not change the parts of speech; both the form remain adjectives. “come” is a verb in “they come late” and if we add an inflectional suffix “ing” we get the form “coming” as in they are coming which is still a verb.
(4) An inflected form can be replaced by another inflected form only
He drink/steal/play etc.
(5) An inflectional suffix occurs at the end position of a form; no further affixation in a form is possible after an inflection. We can say:
root +s -inflectional suffix
develop+ ment +s
(root +derivational suffix+s-inflectional suffix)
develop + s + ment
root inflectional derivational
So, an inflectional suffix is essentially terminal whereas a derivational suffix is not essentially terminal. Derivational suffixes can occur medially and finally but inflectional suffixes occur only finally.
Class –maintaining and class-changing derivational suffixes
Derivational suffixes can be sub-classified into two types:
(1) class-maintaining derivational suffix.
(2) class-changing derivational suffix.
The classes maintaining derivational suffixes are those which produce a derived form of the same class as the underling form, they do not change the class of a part speech. In boyhood, childhood, kinship, friendship, “hood” and “ship” are class-maintaining derivational suffixes. In these examples they produce nouns out of nouns by after suffixation. The class changing derivations are those that produce a derived form of another class. In teacher, boyish, development, national “er” “ish” “ment” “al” are class-changing derivational suffixes. In teacher a verb “teach” has become a noun after suffixing the “er”. In “boyish,” a noun “boy” has become an adjective after suffixing the “ish”. So, it is seen that the derivational suffixes “er” and “ish” change the class of root.