Sentence function basically indicates the purpose of a sentence, rather than sentence form that indicates how it is put together. There are four major types of functions. Declarative sentences are the most common and basic function and express an idea or statement of fact, while interrogative sentences are those that ask a question. An exclamatory sentence has the sentence function of making an exclamatory statement that is not necessarily aimed at anyone else, and an imperative sentence is one in which the statement is a command or instruction.
In many ways, sentence function is the “why?” of a sentence, which deals with why someone is using a particular type of sentence to express something. A declarative sentence is the most common and simple function for sentences to have, and is often considered the base form of a sentence. It can be as simple as “This piece of paper is red,” which serves to simply make a declarative statement about the condition of something. Sentences with a declarative function typically end in a period and when spoken aloud are usually said in a level manner with intonation for emphasis.
Interrogative sentences are statements used to ask questions. Using the base form from before, an interrogative sentence can be made quite simply by shifting the verb within the sentence to become “Is this piece of paper red?” An interrogative sentence function is usually indicated through the use of a question or interrogation mark at the end, and when spoken aloud the speaker often uses rising intonation toward the end of the sentence.
Exclamatory sentences are also a common type of function, in which the statement is meant as an exclamation. It is not necessarily intended for a particular listener, but as a way in which the speaker releases excitement or a particular sentiment. Exclamatory sentences can be as simply as “Yippee!” or “There it is!” and typically end in an exclamation mark. When spoken aloud, sentences with an exclamatory sentence function may be yelled or otherwise are often spoken with higher or faster intonation.
Imperative sentences provide instruction or issue commands. This type of sentence function can be quite short and simple, and can include anything from “Look out!” to “Take one step to the left, now a step back.” Imperative sentences can end in either a period or an exclamation point, based on the nature of the sentence, and may use a steady or loud intonation.