Imperative Sentence:
An imperative sentence is a type of sentence that is used to give someone an order or a command. It is a direct way of expressing a request or instruction.

Structure of an Imperative Sentence:
An imperative sentence typically consists of a simple verb or a verb phrase, without any subject. The subject of the sentence is usually implied to be "you."

Examples of Imperative Sentences:
- "Close the door."
- "Please be quiet."
- "Pass me the salt."
- "Finish your homework."

Key Features of Imperative Sentences:
1. Verb Form: Imperative sentences use the base form of a verb, which means they do not include any tense markers or subject pronouns. For example, "Go" instead of "I go" or "You go."
2. Direct Command: Imperative sentences are straightforward and give direct commands, instructions, or requests.
3. No Subject: The subject of the sentence is usually implied to be "you," even though it is not explicitly stated.
4. Punctuation: Imperative sentences often end with a period (.) or an exclamation mark (!), depending on the tone and intensity of the command.

Function of Imperative Sentences:
Imperative sentences are commonly used in various situations to give orders, commands, or instructions. They can be used to:
- Give directions: "Turn left at the next intersection."
- Issue commands: "Do your chores."
- Make requests: "Please pass me the remote."
- Give advice: "Study hard for the exam."
- Express warnings: "Be careful with that knife."

In conclusion, an imperative sentence is a type of sentence used to give someone an order or a command. It is characterized by its directness, lack of subject pronouns, and use of the base form of a verb.