Suppletion is a term for describing a state in which a word does not follow a set linguistic pattern of usage. For example, when a word has a fixed stem, to which can be attached suffixes or prefixes to denote grammar tense, the flow of declensions or conjugations can be easily understood and used. When a root word does not have suffixes or prefixes to change usage, but instead has another word from different etymology to complete its meaning, this is an irregular usage form, often called suppletion. Irregular verbs and collateral adjectives are often considered a form of suppletion.
Collateral adjectives, sometimes called suppletive adjectives, are adjectives that describe a noun form; however, they are not derived from the noun, as in bovine and cow, which are from two differing word stems. An example of collateral adjectives would be better as compared with good, as these two words come from different root stems of words, yet they have a relationship in completing a meaning. Similarly, irregular verbs in conjugation may have suppletive relationships, as in go and went, as these two verbs also have differing word stems.
Suppletion may take a tense-related form in the past tense, as in the above examples, but in some conjugations nearly every tense is a morphed supply of word stems from differing roots in etymology and yet are, grammatically and in syntax, correct. A common example would be the English verb be. Through its conjugations, it follows tenses as: be, am/are, is, was/were, been, being. This verb comes back to the same root in the past and present participle forms, but the intermediate conjugations have differing word stem roots. As there are no other words that can take the place of these language-morphed words in these tenses, this is considered to be a suppletive verb conjugation.
Because suppletion arouses theories on language changes and morphology and language acquisitions from other languages, they are of particular interest to grammarians and linguists. It has been suggested by linguist Andrew Hippisley that suppletion and frequency of usage may have a bearing on illuminating its usage to lexical storage in the brain. He compared suppletion usage with two competing theories known as the Associative Model and the Combinatorial Model. The evidence from this study point to the Combinatorial Model, which opines that the paradigm of word endings are of primary importance, regardless of the shape of any stem words, and is closer to being the applicable model for predicting suppletion usage.
Irregular paradigms are another example of suppletion in the English language. Although the plural form of dog is dogs, it doesn’t always follow that the plural form of person is necessarily persons, as it is often people. This is why these irregular paradigms are called suppletive paradigms.