The Battle of Grand Gulf was fought on April 29, 1863, during th: In English a sentence may be composed of one or more clauses, that may, in turn, be composed of one or more phrases (e.g. Noun Phrases, Verb Phrases, and Prepositional Phrases). A clause is built around a verb and includes its constituents, such as any NPs and PPs. Within a sentence, there is always at least one main clause (or matrix clause) whereas other clauses are subordinate to a main clause. Subordinate clauses may function as arguments of the verb in the main clause. For example, in the phrase I think (that) you are lying, the main clause is headed by the verb think, the subject is I, but the object of the phrase is the subordinate clause (that) you are lying. The subordinating conjunction that shows that the clause that follows is a subordinate clause, but it is often omitted.[212] Relative clauses are clauses that function as a modifier or specifier to some constituent in the main clause: For example, in the sentence I saw the letter that you received today, the relative clause that you received today specifies the meaning of the word letter, the object of the main clause. Relative clauses can be introduced by the pronouns who, whose, whom and which as well as by that (which can also be omitted.)[213] In contrast to many other Germanic languages there are no major differences between word order in main and subordinate clauses.[214]