Basic English Sentence Patterns
A simple sentence contains only one clause. It includes a single full lexical verb and a combination of some or all of the other clause elements (i.e. subject, object, complement, adverbial). Depending on their structure, sentences might be simple, compound or complex. A compound sentence consists of two or more simple sentences joined together by one of the coordinating conjunctions and, but or so. Each clause in a compound sentence is of equal importance.
In a complex sentence, one or more of the clauses is of lesser importance than the main clauses in a compound sentence. These lesser clauses are called subordinate clauses; they cannot stand on their own. Subordinate clauses can occupy the position of any of the elements in a main clause except the verb. This implies that a subordinate clause might act as a subject, an object, a complement or an adverbial. Subordinate clauses are very often introduced by subordinating conjunctions such as because, when, after, although, as, except or such expressions as in order to, so that, as though or rather than.