Nominal sentence (also known as equational sentence) is a linguistic term that refers to a nonverbal sentence (i.e. a sentence without a finite verb). As a nominal sentence does not have a verbal predicate, it may contain a nominal predicate, an adjectival predicate, in Semitic languages also an adverbial predicate or even a prepositional predicate. In Egyptian-Coptic, however, as in the majority of African languages, sentences with adverbial or prepositional predicate show a distinctly different structure. The relation of nominal sentences to verbal sentences is a question of tense marking. In most languages with nominal sentences such as Russian, Arabic and Hebrew, the copular verb does not surface in indicatival present tense sentences. Conversely, these languages allow the copular verb in non-present sentences.
History
Historically, nominal sentences have posited much controversy regarding their identity as an existent linguistic phenomenon. Ancient grammatical tradition did not uncover such sentences, or if they did, they were only found as an exception to the language structure. This was the view taken by the Western grammatical tradition, which began with an analysis of Ancient Greek followed by an analysis of Latin.
However, this Western/European approach to nominal sentences was not how the Arab grammarians of the early Middle Ages approached it. Arab grammarians did not feel as bound by the classical grammatical categories as did the European counterparts of that historical period. Rather, they viewed a sentence as having two basic categories: 1. a verbal sentence that begins with a verb, and 2. a nominal sentence that begins with a noun and may or may not have a verb within it.
Moving forward in the historical time period, Orientalists later borrowed the nominal sentence terminology from the early Arab grammarians, however modified it slightly to be defined solely with respect to the absence of the verbal predicate, rather than with respect to the first word of the sentence (the noun) that may or may not have a verb in it, as the Arab grammarians defined it. This slight shift in the definition of nominal sentences corresponds partly to both the Western and the Arabic grammar tradition. The Orientalists' definition agrees with the Western grammar's focus of the predicate orientation, and it supports how the Arab grammarians included a sentence category of nominal sentences (nonverbal sentences). Since this new definition of nominal sentences corresponded more accurately to the notion of non-verbal sentences, compared to the Arab definition of it 'may or may not contain a verb', the Orientalists' definition included predicate types other than verbs (nouns, adjectives, etc.).
Syntactic structure and analyses
To successfully account for the syntactic structure of a nominal sentence, there must either be a change in the phrase structure rules or a zero copula must be assumed. This is because nominal sentences cannot be accounted for using traditional phrase structure rules, which state: TP → { NP/ CP} (T) (VP). In other words, a tense phrase must consist of a noun phrase or complementizer phrase, an optional tense head, and a verb phrase. Less technically, this means each sentence must have a noun and verb component. Because there is no overt verb in a nominal sentence, this creates a challenge for the theory.
In the Arabic sentence (), literally "I happy", which is fully grammatical in the language, there is a pronoun, and an adjective, . The first satisfies the sentence requirement of having a noun, but the latter being an adjective, our verb requirement remains unfulfilled. In order to allow this construction, we would have to revise our theory to state *TP → NP { VP/AP} (the * indicates that this is actually an ungrammatical construction), meaning you could have a sentence which breaks down to either a verb phrase or an adjective phrase (see the above figure). However, phrase structure rules are supposed to be universal, therefore this new rule would also allow us to generate "I happy" in English. Since this is not a grammatical, this is an issue that requires attention.
Another problem is that each phrase must consist of a head which bears its name. Therefore, in a verb phrase, the head is always a verb. Again, nominal sentences like do not have a verb, so the verb head position in the verb phrase cannot be filled.
Having a zero copula is one way to solve the problems listed above without compromising the existing syntactic theory. The verb is present, just covertly as "null".