The simplest possible sentence consists of a subject, which controls the action of the verb, and a predicate, which includes the verb and any objects, modifiers, or complements. Written English sentences begin with a capital letter and end with a full-stop punctuation mark (period, exclamation point, or question mark).
Sentences commonly include a variety of phrases and clauses. A phrase is a closely related group of words that lacks both a subject and a verb. In sentences, phrases act as grammatical units, such as subjects, objects, or modifiers.
Unlike a phrase, a clause has both a subject and verb. An independent clause can stand on its own as a complete sentence. A dependent clause must be attached to an independent clause to make sense. Like phrases, clauses can act as subjects, objects, or modifiers.
By stringing phrases and clauses together, we can create a variety of sentence types. A compound sentence has at least two independent clauses joined by a conjunction. A compound-complex sentence has at least two independent clauses plus at least one dependent clause.
Sentences are also classified by mood. A declarative sentence makes a statement. An interrogative sentence asks a question. An imperative sentence gives a command. Sentences also have voice (active or passive), which determines whether the subject of the sentence is doing or receiving the action of the main verb.