A sentence is a grammatically complete group of words that expresses a thought. Words in a sentence can be identified by parts of speech, but you should also understand how words and phrases function in sentences.

Recognizing subjects and predicates

To be grammatically complete, a sentence must contain both a subject, which identifies what the sentence is about, and a predicate, which says or asks something about the subject or tells the subject to do something.

Some sentences contain only a one-word predicate with an implied subject; for example, Stop! is a complete sentence, with the unspoken subject you. Most sentences, however, contain some words that expand upon the basic subject and predicate.

The central elements of subjects and predicates are nouns and verbs.

Using conventional English word order

In general, subjects, verbs, and objects must all be placed in specific positions within a sentence.

The only word in this sentence that you can move to different locations is the adverb reluctantly (Mario reluctantly left Venice or Reluctantly, Mario left Venice). The three key elements of subject, verb, and object rarely move out of their normal order.

Recognizing sentence patterns

Knowing a word’s part of speech helps you understand how to use it, but you also have to look at the part it plays in a particular sentence. In the following sentences, the noun description plays different roles:

In the first sentence, description serves as the subject of the verb conveys, while in the second it serves as the direct object of the verb read.