In traditionalgrammar, asubject complement is apredicative expression that follows acopula (commonly known as alinking verb), whichcomplements thesubject of aclause by means of characterization that completes the meaning of the subject.[1]
When anoun,noun phrase, orpronoun functions as a subject complement, it is called apredicative nominal. When anadjective or analogous phrase functions as subject complement, it is called apredicative adjective. In either case thepredicative complement corresponds to the subject.
Within the small class of copulas that preface a subject complement, the verbbe, or one of its concomitant forms, is the most common. Because a copula is anintransitive verb, subject complements are not customarily construed to be theobject of the verb. They are often deemed to be neitherarguments noradjuncts of a predicate. A plural or singular subject, rather than a subject complement determines thegrammatical number expressed by a copula.[2][3]
The subject complement is bold in the following examples:
Here,was is a copula (a concomitant form ofbe) that links the subject complementa tranquil pool (which has thehead nounpool), to the subjectthe lake (which has the head nounlake).
In this example,tranquil is a predicative adjective linked to the subjectthe lake via the copulais (another concomitant form ofbe).[4]
An example in which the subject complement is a clause is:
In some languages, adjectives arestative verbs and do not require a copula in predicative use.
Eighteenth-century grammarians such asJoseph Priestley justified the colloquial usage of subject complements in instances such asit is me (andit is him,he is taller than him, etc.) on the grounds that good writers use it often:
All our grammarians say, that the nominative cases of pronouns ought to follow the verb substantive as well as precede it; yet any familiar forms of speech and the example of some of our best writers would lead us to make a contrary rule; or, at least, would leave us at liberty to adopt which we liked best.[5]
Other grammarians, including Baker (1770), Campbell (1776), andLindley Murray (1795), say the first person pronoun must beI rather thanme because it is anominative that is equivalent to the subject. The opinions of these three partisans of the nominative case were accepted by the schoolmasters.[6][verification needed] However, modern grammarians such asRodney Huddleston andGeoffrey K. Pullum deny that such a rule exists in English and claim that such opinions "confuse correctness with formality".[7]
This argument forit is I is based on the model of Latin, where the complement of the finite copula is always in thenominative case (and where, unlike English, nominative andaccusative are distinguishedmorphologically in all nominal parts of speech and not just in pronouns).[8] The situation in English may, however, also be compared with that of French, where the historical accusative formmoi functions as a so-calleddisjunctive pronoun, and appears as a subject complement (c'est moi, 'it is me'). Similarly, the clitic accusative form can serve as a subject complement as well as a direct object (il l'est 'he is [that/it]', cf.il l'aime 'he loves it').
Fiction writers have occasionally pointed out the colloquialisms of their characters in an authorial comment. In "The Curse of the Golden Cross", for example,G. K. Chesterton writes, "'He may be me,' saidFather Brown, with cheerful contempt for grammar." And inThe Lion, the Witch and the Wardrobe,C. S. Lewis writes, "'Come out, Mrs. Beaver. Come out, Sons and Daughters of Adam. It's all right! It isn't Her!' This was bad grammar of course, but that is how beavers talk when they are excited."