In English, every sentence must contain at least one clause. A clause is a group of words that has a predicate and a subject. The subject is the place, person or thing that the entire sentence is about. The predicate includes the verb and other words that describe or elaborate on the verb.
There are two main types of clauses in English grammar: independent and dependent. The independent clause in a sentence is also known as the "main clause." There are two types of dependent clauses: "subordinate clauses" and "relative clauses."
An independent clause makes a complete thought and can make up a complete sentence by itself. This type of clause does not require anything else to make a sufficient sentence. More than one independent clause can be combined to make a compound sentence using coordinating conjunctions. Coordinating conjunctions include: "and," "but," "yet," "or" and "nor." Independent clauses can also be joined by semicolons. The semicolon can be used with or without a conjunctive adverb, such as: "nevertheless," "moreover," "on the other hand" or "however."
A dependent clause is one that cannot stand alone and needs the support of a main clause or independent clause. Dependent clauses typically begin with either a relative pronoun or a subordinating conjunction. Dependent clauses that start with a relative pronoun are known as "relative clauses." Relative nouns include: "who," "that," "which," and "whomever." Relative clauses act as an adjective in the sentence by modifying nouns, pronouns or noun phrases. Dependent clauses that begin with subordinating conjunctions are known as "subordinate clauses." Subordinating conjunctions include: "because," "though," "until," "whether," "while," "before" and "after." Subordinate clauses act like adverbs in the sentence by modifying verbs, adjectives or adverbs. Subordinate clauses may modify the entire main clause in a sentence. When a subordinate clause comes before the main clause in a sentence, it must be separated with a comma.