A sentence is a grammatical unit that is composed of one or more clauses and phrases. English has four main sentence types: declarative, interrogative, imperative, and conditional sentences.

• Declarative Sentences are used to form statements.
• Interrogative Sentences are used to ask questions.
• Imperative Sentences are used for commands.
• Exclamatory Sentences used to express strong feelings.

Here is a site that contains several examples.
http://homeworks-edsci.blogspot.com/2009/09/kinds-of-sentences_15.html

What Makes a Sentence?

Hello fellows! Since our next lesson is about sentences, I want to share with you the basic components of sentences; these are phrases and clauses. A phrase is a group or collection of related words that may have nouns or verbals, but does not include a subject and a verb. While a clause is a collection of words that has a subject that is actively doing a verb. Here are some examples for you to understand phrases and clauses further.

http://www.prismnet.com/~hcexres/style/phrases_clauses.html

Interjections

Hello guys! How are you doing? I am so glad we finally surpassed our first long exam.

I hope we all get good results. :)

Interjection or also known as exclamation is a word used to express a feeling or sentiment of the speaker and is usually placed at the beginning of a sentence. Interjections are commonly followed by an exclamation mark "!".

(e.g "Excuse me!", "Sorry!", "No thank you!", "Oh dear!", "Hey that's mine!")