I introduced the idea that some complex words have meanings that are so predictable that they do not have to be listed in a dictionary. Such words illustrate the fact that a word need not be a lexical item (while, conversely, idioms illustrate the fact that a lexical item need not be a word). However, I did not discuss the different varieties of non-lexical-item words. We will focus on one variety: words that do not have to be listed because they are merely grammatically conditioned variants of a word that is more basic, in some sense – and which itself may or may not be listed, depending on whether its meaning is predictable or not.

By way of illustrating the notions ‘more basic’ and ‘grammatically conditioned variant’, let us consider the words performs, performed and performance in (1)–(3):

(1) This pianist performs in the local hall every week.

(2) Mary told us that this pianist performed in the local hall every week.

(3) The performance last week was particularly impressive.

All these words contain a suffix: perform-s, perform-ed, and perform-ance. However, the suffixes -s and -ed are dependent on the grammatical context in a way that the suffix -ance is not.

In (1), the reason why the verb perform has an -s suffix is that the subject of the verb (the noun phrase denoting the person doing the performing) is singular (this pianist), not plural (these pianists). (For more on grammatical terms such as ‘subject’, you may consult the syntax volume in the ETOTEL series.) It is easy for a native speaker to check that (4) and (5) ‘feel wrong’:

(4) *This pianist perform in the local hall every week.

(5) *These pianists performs in the local hall every week.

(You are reminded that the asterisk indicates that a sentence is unacceptable for some reason to do with grammar or with the structure of the language generally, rather than for reasons such as truthfulness or politeness.) Examples (4) and (5) are unacceptable because they violate a grammatical rule of English concerning ‘agreement’ between a verb and its subject: the -s suffix on the verb is obligatory when the subject is a singular noun phrase (that is, one for which he, she or it could be substituted), and forbidden when the subject is a plural noun phrase (one for which they could be substituted). The -s on the verb in (1) does not make any independent contribution to the meaning of the sentence, one might say; it simply reflects the fact that the subject of the sentence is singular rather than plural.

In (2), the aspect of the grammatical context that is relevant to the suffix -ed on performed is the fact that the verb told is in the past tense (that is, it refers to a past event, namely an earlier conversation with Mary). Mary’s actual words in this earlier conversation were probably ‘This pianist performs …’, not ‘This pianist performed …’. Why then is the word performs replaced by performed in the report of her words at (2)? The answer is that English grammar incorporates a rule about what is called ‘sequence of tenses’: if a verb of saying or thinking is in the past tense (as told is here), then a verb in any sentence reported as having been said or thought is likely to be shifted backwards in tense, so to speak: performs is replaced by performed, performed in turn is replaced by had performed, and will perform is replaced by would perform. Again, the -ed on performed does not make any independent contribution to the meaning of the sentence – for example, it does not (as one might expect) indicate that the series of concerts has ceased since the conversation with Mary took place. Instead, it is merely a grammatical consequence of the fact that the verb of saying is in the past tense (told) rather than the present (tells).

In (3), on the other hand, there is no grammatical factor that requires the presence of -ance on performance. The most one can say is that, in the context where performance occurs, one expects to find a noun rather than a verb such as perform, as illustrated by the unacceptability of (6):

(6) *The perform last week was particularly impressive.

However, there is nothing in this context that forces us to choose the noun performance in particular, or even another noun with the suffix -ance. Any noun (or at least any noun with an appropriate meaning) will do, as in:

(7) The performer last week was particularly impressive.

(8) The concert last week was particularly impressive.

We can describe the difference between performance on the one hand and performs and performed on the other by saying that the latter pair are grammatically conditioned variant forms of the verb perform, whereas performance is not a variant form of the verb, but rather a noun derived from it. We have encountered here another important distinction: between derivational morphology, and so called inflectional morphology or inflection, which deals with the inflected forms of words, that is the kind of variation that words exhibit on the basis of their grammatical context. We will look in more detail at inflection in English.

It is necessary first, however, to introduce some terms that are more precise than the ordinary term ‘word’, which I have relied on heavily up to now. I have called performs and performed ‘grammatically conditioned variants’ or ‘inflected forms’ of ‘the verb perform’. But if one compares (1) with (9), alongside the unacceptable examples (4) and (5), one can see that perform itself deserves to be called a grammatically conditioned variant too:

(9) These pianists perform in the local hall every week.

The fact that the verb appears with no suffix in (9), where the subject these pianists is plural, is just as much a matter of grammar as the fact that the verb appears with -s in (1), where the subject is singular. But it is awkward and confusing to describe perform in (9) as a form of itself ! We need a new term for the more abstract kind of word of which the word forms performs, performed and perform are all inflectional variants. Let us call this more abstract kind of word a lexeme. Let us also introduce the convention that, where the distinction is important, words as lexemes are written in small capitals, while words as inflected forms continue to be represented in italics. We can now say that performs, performed and perform are all inflected forms of the lexeme PERFORM, and we can describe the grammatical function of performed by calling it the past tense form of the verb PERFORM. Equally, told in (2) is the past tense form of the verb TELL, and pianists in (9) is the plural form of the lexeme PIANIST.

Being abstract in this sense, a lexeme is not strictly speaking something that can be uttered or pronounced; only the word forms that belong to it can be. (For that reason, one could just as well use PERFORMS or PERFORMED as the label for the lexeme PERFORM; but, by convention, we refer to lexemes in English by means of their bare, unaffixed forms.) The most straightforward way to define the term word form is to tie it so closely to pronunciation that pronunciation is its sole criterion: two word forms are the same if and only if they are pronounced the same, or are homophonous. (Let us not be sidetracked by the fact that two words can be pronounced the same but spelled differently in English, and vice versa; in most domains of linguistic research, spoken language is more important than written.) It follows that the same word form can belong to two quite different lexemes, as does rows in (10) and (11):

(10) There were four rows of seats.

(11) One person rows the boat.

In (10), rows is the plural of the noun ROW meaning ‘line of people or things’, while in (11) it is one of the present tense forms of the verb ROW meaning ‘propel with oars’ (more precisely, it is the form used with subjects that can be replaced by he, she or it : so-called ‘third person singular’ subjects). Let us use the term grammatical word for designations like ‘the plural of the noun ROW’, ‘the third person singular present tense of the verb ROW’, and ‘the past tense of the verb PERFORM . It will be seen that one lexeme may be represented by more than one word form, and one word form may represent more than one lexeme; what links a word form with a lexeme in a given context is the grammatical word that the word form expresses there. This may seem complicated at first, but as we discuss English inflection in more detail you will (I hope) come to appreciate the usefulness of these distinctions.