In gapping, a verb is removed from one clause due to its presence in another, though the meaning remains clear. A simple example of this is in a sentence like “Bob plays the piano, Lisa the guitar,” in which the word “plays” has been omitted in the second clause. The reader of this sentence is able to understand what is meant and infer the verb in the second clause, though it is completely removed. Gapping occurs in the final usage in languages that are constructed as Subject-Verb-Object (SVO), but is often found in the first clause in languages that are Subject-Object-Verb (SOV).
The importance of gapping in language is that it clearly indicates that important elements of a clause can be missing without inherently destroying meaning. This removal has to be done carefully, however, or else meaning can be obfuscated or otherwise interfered with in a sentence. For gapping to be performed properly, there should be only a single verb in use, to ensure that meaning remains clear even with a gap. For example, “I read one book last week, but my sister – two!” is clear in terms of meaning because there is only a single verb.
In the previous example, punctuation was used to indicate where the gap exists, but this is not always required in gapping. The use of two or more verbs in adjoining clauses typically makes a sentence grammatically flawed for the use of gapping, as the meaning can too easily become obscured. For example, in a sentence like “Bob learned that his sister runs quickly, his brother slowly,” there is too much opportunity for confusion. There is a gap in the final clause, but there are two potential verbs that can go there: either “learned” or “runs.” While it can be assumed that the gap is “runs,” this is a grammatically flawed sentence.
Gapping reveals quite a bit about how language is assembled and how speakers and listeners are able to use it in communication. The structure of the gap in the final part of a sentence, such as that found in English, exists in languages that are constructed as Subject-Verb-Object or SVO. English sentences typically begin with a subject, then a verb that indicates action, and finally the object it is performed upon. Other languages, such as Japanese and Korean, are constructed as Subject-Object-Verb or SOV sentences. In SOV languages, gapping is performed in the first clause, and the one that follows indicates the missing verb.