The declarative sentence is the most common kind of sentence in language, in most situations, and in a way can be considered the default function of a sentence. What this means essentially is that when a language modifies a sentence in order to form a question or give a command, the base form will always be the declarative. In its most basic sense, a declarative states an idea (either objectively or subjectively on the part of the speaker; and may be either true or false) for the sheer purpose of transferring intel. In writing, a statement will end with a period.
This is a companion discussion topic for the original entry at http://grammarerror.com/tags/declarative-sentence