Sentence

a construction in which constituents are combined according to the rules of grammar.

According to Crystal, the following are true of any sentence in English:
 * 1) Every sentence must adhere to the rules of grammar.


 * 1) A sentence must be complete by itself, i.e. it must contain at least one independent clause.
 * 2) A sentence is the largest construction that grammar applies to.

Components
Every sentence must contain
 * Subject : a noun [phrase], pronoun, or clause
 * Verb :  the action or state of being expressed by the sentence

A sentence may also contain:
 * Object : a noun or nouns affected by the verb in the sentence  (see Direct Object and Indirect Object)
 * Complement :  a noun [phrase], pronoun, or clause that gives more information about the subject or object
 * Adverbial : (aka Circumstantial) a word or phrase that provides more information, such as the time or place

Crystal, David. Rediscover Grammar. pages 36-37.