In language, a clause is a constituent or phrase that comprises a semantic predicand (expressed or not) and a semantic predicate. A typical clause consists of a subject and a syntactic predicate, the latter typically a verb phrase composed of a verb with or without any objects and other modifiers. However, the subject is sometimes unexpressed if it is easily deducible from the context, especially in null-subject languages but also in other languages, including instances of the imperative mood in English.

A complete simple sentence contains a single clause with a finite verb. Complex sentences contain at least one clause subordinated to (dependent on) an independent clause (one that could stand alone as a simple sentence), which may be co-ordinated with other independents with or without dependents. Some dependent clauses are non-finite, i.e. they do not contain any element/verb marking a specific tense.

A clause that contains one or more dependent or subordinate clauses is called a matrix clause. A matrix clause can be the main clause or any subordinate clause that itself contains one or more (additional) subordinate clauses.^{[citation needed]}

A primary division for the discussion of clauses is the distinction between independent clauses and dependent clauses. An independent clause can stand alone, i.e. it can constitute a complete sentence by itself. A dependent clause, by contrast, relies on an independent clause's presence to be efficiently utilizable.

A second significant distinction concerns the difference between finite and non-finite clauses. A finite clause contains a structurally central finite verb, whereas the structurally central word of a non-finite clause is often a non-finite verb. Traditional grammar focuses on finite clauses, the awareness of non-finite clauses having arisen much later in connection with the modern study of syntax. The discussion here also focuses on finite clauses, although some aspects of non-finite clauses are considered further below.

Clauses can be classified according to a distinctive trait that is a prominent characteristic of their syntactic form. The position of the finite verb is one major trait used for classification, and the appearance of a specific type of focusing word (e.g. Wh-word) is another. These two criteria overlap to an extent, which means that often no single aspect of syntactic form is always decisive in deciding how the clause functions. There are, however, strong tendencies.

Standard SV-clauses (subject-verb) are the norm in English. They are usually declarative (as opposed to exclamative, imperative, or interrogative); they express information neutrally, e.g.

Declarative clauses like these are by far the most frequently occurring type of clause in any language. They can be viewed as basic, with other clause types being derived from them. Standard SV-clauses can also be interrogative or exclamative, however, given the appropriate intonation contour and/or the appearance of a question word, e.g.