What is a Sentence?

This is a question that can be answered in many different ways but, at its simplest, a sentence will express a complete thought or idea. The following sentence shows a complete idea:

This is a sentence.

When we look at the structure of the sentence, we can break it down into parts such as words, and, even phrases. Each word can be grouped under different parts of speech such as noun or verb and so on. However, every sentence needs at least one finite verb. Without a finite verb, a sentence does not exist. What is usually in a sentence is also a subject and, sometimes but not always, an object. This combination of subject and finite verb forms a clause. A clause that can stand alone is an independent clause. This independent clause on its own can form a simple sentence. However, if you combine two independent clauses with a co-ordinating conjunction, you have a compound sentence and, if you have an independent clause with a dependent clause, you can make a complex sentence.