Most countable nouns in English have two word forms: a singular and a plural. Inflectionally, for any noun lexeme X, there are just two grammatical words, ‘singular of X’ and ‘plural of X’, contrasting in number. Thus, to the lexeme CAT there corresponds a singular form cat, consisting of just one morpheme, and a plural form cats, consisting of a root cat and the suffix -s. This suffix and its allomorphs were discussed, and we have noted that -s is the regular suffix for forming plurals. Irregular suffixes expressing plurality include -i, -ae and -a (as in cacti, formulae, phenomena) found with some relatively learned words borrowed from Latin or Greek; the suffix -(r)en that shows up only in oxen, children and brethren; and a very few others such as the Hebrew -im in cherubim and kibbutzim.

There are also some countable nouns that express their plural with no suffix at all. I have already mentioned two (teeth, men) where there is a change in the vowel of the root – or, more precisely, an allomorph of the root with a different vowel from the singular. However, there are also some whose plurals display not even a vowel change: for example, sheep, fish, deer, trout. An obvious question, therefore, is: if the plural and singular forms of these nouns are the same, how can we tell whether they are singular or plural? The answer is: according to the syntactic context. Consider the following examples:

(12) A deer was visible through the trees.

(13) Two deer were visible through the trees.

In (12) we can tell that deer is singular (more strictly, it represents the grammatical word ‘singular of the lexeme DEER’) because it is accompanied by the indefinite article a, which only ever accompanies singular nouns (e.g. a cat, not *a cats), and because the form of BE found in (12), agreeing in singular number with the subject a deer, is was, not were. In (13), for parallel reasons, we can tell that deer is plural: the numeral two accompanies only plural nouns (two cats, not *two cat), and the form of BE in (13) is the plural were.

The class of nouns which are unchanged in the plural (sometimes called ‘zero-plural’ nouns, if they are analyzed as carrying a ‘zero suffix’) could conceivably be just as random as the class of those with vowel change (tooth, man, etc.). But in fact there seems to be a common semantic factor among the zero-plurals: they all denote animals, birds or fish that are either domesticated (SHEEP) or hunted (DEER), usually for food (TROUT, COD, PHEASANT). It is true that the relationship is not hard and-fast: there are plenty of domesticated and game animals which have regular -s plurals (e.g. COW, GOAT, PIGEON, HEN). Nevertheless, the correlation is sufficiently close to justify regarding zero-plurals as in some degree regular, obeying a minority pattern of plural formation that competes with the dominant pattern of -s-suffixation.

I made the point that only some nouns have plural forms, namely nouns that refer to entities that are countable. That is why the forms cats and pianists exist, but not *astonishments or *rices – except perhaps in contexts where they can be interpreted as denoting countable entities, such as astonishing events or varieties of rice. But does that mean that all nouns referring to countable entities have both singular and plural forms? Not quite. There are a few nouns such as SCISSORS and PANTS which exist only in an -s-plural form, and which appear only in plural syntactic contexts, even though they denote single countable entities, as is shown by the contrast between (14) and (15):

(14) a. Those scissors belong in the top drawer.

        b. Your pants have a hole in the seat.

(15) a. *That scissors belongs in the top drawer.

        b. *Your pants has a hole in the seat.

This idiosyncratic lack of a morphological singular form (except in compounds such as scissor factory) creates a problem in contexts where the syntax seems to require such a form, as when the noun is preceded by the indefinite article a or an. We can say neither *a scissor nor *a scissors, and likewise neither *a pant nor *a pants. However, for these lexemes, there is a conventional circumlocution or periphrastic form: pair of pants and pair of scissors (as in That pair of scissors belongs in the top drawer).

The unusual nouns SCISSORS and PANTS provide an opportunity to deal with a possible doubt concerning whether the singular–plural contrast in nouns really deserves to be called inflectional. If inflection is a matter of grammatically conditioned variation, as I said, it is easy to agree that (say) the contrast between performs in (1) (This pianist performs …) and perform in (9) (These pianists perform …) is inflectional, because it is a contrast imposed by the grammatical context (whether the subject noun phrase is singular or plural). But what about the noun phrases themselves? The choice between singular and plural there is determined not by grammar but by meaning, one may think – by what the speaker wants to say. If so, does this contrast really deserve to be called grammatically conditioned?

Despite the freedom to choose between, say, this pianist and these pianists as subjects of (9), there is still a sense in which English grammar affects the choice between singular and plural. It does so in the sense that it imposes the choice. In talking about a series of weekly piano concerts, we are free to be vague about the number of pianists who perform – except that we are forced by English grammar to be precise about whether there is one (that pianist) or more than one (these pianists). Likewise, if I see a cat or some cats in the garden, I cannot report what I have seen without making it clear whether there was just one cat, as in (16) or more than one cat, as in (17). A formulation that is deliberately vague on that issue, such as (18), is unacceptable:

(16) I saw a cat in the garden.

(17) I saw (some) cats in the garden.

(18) *I saw cat in the garden.

The best we can do to express the intended content of (18) is use a circumlocution like one or more cats or at least one cat. In this respect, English grammar contrasts with that of, for example, Chinese, where the singular–plural contrast is not expressed morphologically in nouns or verbs, and indeed is scarcely grammatically relevant at all. That does not mean that one cannot distinguish between one object and several when talking Chinese; it is just that the distinction is not imposed by Chinese grammar, which permits ambivalence about plurality. Curiously, the only nouns with which Chinese-style ambivalence is permissible in English are the unusual plural-only ones such as SCISSORS. Compare the meaning of (14a) with that of (19) and (20):

(19) That pair of scissors belongs in the top drawer.

(20) Those pairs of scissors belong in the top drawer.

(19) and (20) make it plain whether one or more than one pair of scissors is being talked about. On the other hand, (14a) is vague in just the way that (17) was meant to be; it can be interpreted as synonymous with either (19) or (20).

The singular–plural distinction is the only grammatical distinction that is expressed morphologically in English nouns. Some readers (especially those that know something of languages such as German or Latin) may be surprised that I have said nothing about the ‘apostrophe-s’ form: pianist’s, man’s, child’s, children’s etc. – do these not count as further inflected forms of the lexemes PIANIST, MAN and CHILD, namely ‘possessive’ forms? However, it is easy to show that what -’s attaches itself to is not a morphological unit such as noun root (e.g. man) but a syntactic unit, namely a noun phrase:

(21) that man’s bicycle

(22) that old man’s bicycle

(23) that man next door’s bicycle

(24) that man you met yesterday’s bicycle

(25) that man you met’s bicycle

Examples (21), (22) and (23) may seem compatible with saying that -’s is an affix that attaches to nouns, but (23) should give us pause (after all, it is the man, not the door, that owns the bicycle!), and (24) and (25) show conclusively that what -’s attaches to is a whole noun phrase (that man you met (yesterday)), including whatever modifiers it may contain following the noun at its head (man, in this instance). So -’s belongs in the study of syntax, not morphology. Its only morphological peculiarity is that, when the word immediately before it is a noun with the plural suffix -s, the two fuse, both in pronunciation and spelling, written -s’ : e.g. these pianists’ performances, not *these pianists’s performances.