Sentence

A sentence is a group of words that are joined together to mean something. It is the basic unit of language and expresses a complete thought. It does so by following the grammatical basic rules of syntax: Ram is walking.

A complete sentence has at least a subject and a main verb to state (declare) a complete thought: She walks. A subject is the noun (name) that does the main verb. The main verb is the activity that the subject does. 

In English and many other languages, the first word of a written sentence has a capital letter. At the end of the sentence there is a punctuation mark depending on whether it is a statement, a question, a command, a request or an exclamation.

 Phrases and clauses 
A phrase or clause is part of a sentence.McArthur, Tom (ed) 1992. The Oxford companion to the English language. Oxford University Press.p773–777

This is an example of a sentence:
 The dog is happy.
In this sentence, The dog is the subject, and is is the verb.

This is an example of a phrase:
 The happy dog

There is no verb and so we do not know anything about what the happy dog is doing. Therefore, it is not a sentence.

A clause is a sentence within a sentence:
 They milked the cows, and then they made cheese and butter. This sentence has two co-ordinate (equal) clauses, linked by and.p220

Types of sentence
 A simple sentence has only one clause and one independent variable: The cat is sleeping.
 A compound sentence has two or more clauses, which are joined with conjunctions, punctuation, or both: The dog is happy, but the cat is sad.
 A complex sentence has one clause with a relative clause: The dog, which is eating the bone, is happy.
 A complex-compound sentence (or compound-complex sentence) has many clauses, at least one of which is a relative clause: The dog, which is eating the bone, is happy, but the cat is sad.

Sentences have different purposes:
 A declarative sentence, or declaration, is the most common type of sentence. It tells something. It ends with a full stop . (The dog is happy.)
 An interrogative sentence, or question, asks something. It ends with a question mark ? (Are you happy?)
 An exclamatory sentence, or exclamation, says something out of the ordinary. It ends with an exclamation mark ! (That dog is the happiest dog I have ever seen!)
 An imperative sentence, or command, tells someone to do something. It ends with a full stop . (Give the dog a bone.)

 Basic English sentences 
Here are some sentences written in Basic English:

The sky is blue.

Today is Monday.

Tomorrow is Tuesday.

The baby is smiling.

Sheila is reading a book.

This is the road to take.

Read a book about the history of America.

There are beautiful flowers growing in the garden.

The cushions are new and I feel the comfort they give me.

They are playing in the grounds.

Related pages
 Phrase
 Punctuation
 Word

 References 

Other websites
TYpes of sentences worksheet