A declarative sentence is a sentence whose purpose is to make a statement. The presence of a period at the end of the sentence signifies that it is declarative, provided the writer is using punctuation properly. Declarative sentences are the simplest sentences to learn and have a predictable structure.
In their simplest form, declarative sentences take the SVO, or subject-verb-object, format. The subject of the sentence is the one performing the action. The verb of the sentence represents the action, and the object is the entity receiving the action. Other types of sentences are interrogative sentences, imperative sentences and exclamation sentences.