Regular and irregular inflection

At the beginning, I introduced the topic of inflection by way of the distinction drawn between words that have to be listed in a dictionary and words that do not. I said that one does not have to list performs and performed alongside perform, or pianists alongside pianist, because they are merely grammatically conditioned variants of one basic word – of one lexeme, in fact. But it is not correct to say that dictionaries never have anything to say about inflectional morphology. This is because there are two reasons why a word form such as pianists does not have to be listed, and these reasons are independent. The first is that, once we know that an English word is a noun denoting a kind of thing that can be counted (if the noun is PIANIST or CAT, perhaps, but not ASTONISHMENT or RICE), then we can be confident that it will have a plural form with no idiosyncrasies of meaning: it will mean simply ‘more than one X’, whatever X may be. The second reason is that, unless otherwise specified, we can be confident that the plural form of any countable noun will be formed by adding to the singular form the suffix -s (or rather, the appropriate allomorph of this suffix); in other words, suffixing -s is the regular method of forming plurals.

That qualification ‘unless otherwise specified’ is crucial, however. Any native speaker of English, after a moment’s thought, should be able to think of at least two or three nouns that form their plural in some other way than by adding -s: for example, CHILD has the plural form children, TOOTH has the plural teeth, and MAN has the plural men. The complete list of such nouns in English is not long, but it includes some that are extremely common. What this means for the dictionary entries for CHILD, TOOTH, MAN and the others is that, although nothing has to be said either about the fact that these nouns possess a plural form or about what it means, something does have to be said about how the plural is formed. Thus, for example, a dictionary entry for TOOTH will look like this:

tooth noun (plural teeth). One of a set of hard white structures set in the jaw and used for biting and chewing.

Such nouns, in short, are irregular in their plural formation, and irregularity is a kind of idiosyncrasy that dictionaries need to acknowledge by indications such as ‘(plural teeth)’ here. One can easily visualize a variety of English with no irregularity, but this would be unlike any variety actually in use. Readers of George Orwell’s novel Nineteen Eighty-Four will recall that, in the politically purged variety of English called Newspeak, Orwell envisages the eradication of morphological irregularity along with opportunities for ‘thoughtcrime’, so that the plural of MAN in Newspeak is not men but mans. In reality as opposed to fiction, this sort of regularization is a well-known feature of the speech of young children and of non-native learners. The very fact that regularization takes place confirms that there is something about the irregular forms that requires them to be specially learned.

For English nouns, there is no difficulty in determining which is the regular method for forming the plural. However, the very fact that there is more than one method raises a potentially tricky question about morphemes and their allomorphs. The allomorphs of a morpheme may be distributed in a fashion that requires reference to individual lexical items, and also that allomorphs may differ from each other phonologically in idiosyncratic ways (as -duce differs from -duct-, and -sume from -sump-). If all this does not inhibit us from recognizing them as allomorphs of one morpheme, what about the different plural suffixes exhibited by nouns such as pianists, oxen, formulae and cacti (these last three corresponding to the singular forms ox, formula and cactus)? Can we not classify -s, -en, -ae and -i as all allomorphs of a single ‘plural’ morpheme? Should we not also recognize a further allomorph that we might call ‘vowel change’, to accommodate men and teeth, which lack a suffix? Admittedly, these allomorphs are quite unlike each other in pronunciation – but if allomorphs are allowed to be differ somewhat, why cannot we allow them to be differ considerably? At what point, if any, does phonological divergence become too great?

This is a difficult question. Discussing it adequately would take us beyond the bounds of an elementary textbook on English word-structure. I mention it here in order to alert readers to be careful, when reading any text in which the term ‘morpheme’ is used, to make sure they understand how the author is using it: whether in a more concrete sense, oriented towards pronunciation (in terms of which -s, -en, -ae and -i represent different morphemes), or a more abstract sense, oriented towards meaning or grammatical function (in terms of which -s, -en, -ae and -i are all allomorphs of one morpheme). A good way to avoid any confusion is to use terms such as ‘root’, ‘suffix’ and ‘prefix’, wherever possible, rather than ‘morpheme’. This is because, although there may be disagreement about whether to treat these plural suffixes as allomorphs of one morpheme, everyone agrees that they are distinct suffixes.

This question about suffixes with the same grammatical function has a bearing also on allomorphy affecting roots, such as wife and wive-. The phonological similarity between wife and wive-, and the fact that parallel alternations can be found (e.g. knife and knive-, path and path-, house and house-, in all of which a voiceless fricative consonant in the singular alternates with its voiced counterpart in the plural) are solid grounds for calling them allomorphs of one morpheme. We clearly want to recognize wife and wives as expressing the singular and plural respectively of one lexeme WIFE. But does it follow that all the word forms of a lexeme must always share the same root morpheme? Does it ever happen that two word forms that behave grammatically like forms of one lexeme look so dissimilar that they seem to have no root morpheme in common (at least if ‘morpheme’ is given its more concrete sense)?

The answer is yes, but seldom (at least in English). Consider the lexeme GO. Because it is a verb, we expect it to have a past tense form, and this expectation is not disappointed. Surprisingly, however, what functions as the past tense form, namely went, is phonologically quite dissimilar to the verb’s other forms go, goes, going and gone. Should we say, then, that go and went are allomorphs of one morpheme? Most linguists would say no; rather, they would treat this as showing that one lexeme may be represented by two (or more) quite distinct root morphemes (not allomorphs). The term given to this phenomenon is suppletion; go and went are said to be distinct roots (and hence distinct morphemes), standing in a suppletive relationship as representatives, in different grammatical contexts, of one lexeme. This view of suppletion, as a relationship between roots rather than between allomorphs, is consistent with the ‘concrete’ view of allomorphy outlined just now in relation to the plural suffixes.

From the point of view of allomorphy, it may seem that go and went- stand in just the same relationship as the plural suffixes -s, -en, -ae and -i; hence, if the term ‘suppletion’ is used for the former relationship, it should be used for the latter too. In fact, however, ‘suppletion’ is generally applied only to roots, not to affixes. This is because suppletion is generally seen as a relationship between forms of the same lexeme, whereas allomorphy need not be. For example, the allomorphs wife and wive- show up in forms of the lexeme WIFE, but the plural allomorphs [s], [z] and [Iz] do not belong to any one lexeme – rather, they intersect with noun lexemes in such a way that any one regular noun chooses just one of these allomorphs, on the basis of the phonological criteria.

The discussion so far has been rather general. In the remaining topics I will put flesh on the bones by discussing in more detail how inflection works in English, i.e. what grammatical words are associated with inflected lexemes, how these grammatical words are regularly expressed, and what kinds of irregularity they may display. Because the role of inflectional morphology in English is much smaller than in languages such as German or Russian (although greater than in Chinese), what needs to be said about each wordclass is relatively circumscribed. However, we will provide opportunities to illustrate a few further general issues and notions as well.