The Sentence

1. When we speak or write we use words. We generally use these words in groups; as,
Little Jack Homer sat in a corner.
A group of words like this, which makes complete sense, is called a Sentence.

Kinds of Sentences

2. Sentences are of four kinds:
(1) Those which make statements or assertions; as, Humpty Dumpty sat on a wall.

(2) Those which ask questions; as Where do you live?

(3) Those which express commands, requests, or entreaties; as,
Be quiet.
Have mercy upon us.

(4) Those which express strong feelings; as,
How cold the night is!
What a shame!

A sentence that makes a statement or assertion is called a Declarative or Assertive
sentence.
A sentence that asks a question is called an Interrogative sentence.
A sentence that expresses a command or an entreaty is called an Imperative sentence.
A sentence that expresses strong feeling is called an Exclamatory sentence.

taken from: High School English Grammar and Composition by Wren and Martin

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