Definition

A sentence is the largest unit of any language. In English, it begins with a capital letter and ends with a full-stop, or a question mark, or an exclamation mark.

The sentence is generally defined as a word or a group of words that expresses a thorough idea by giving a statement/order, or asking a question, or exclaiming.

Example:

He is a good boy (statement), Is he a good boy? (question), What a nice weather! (exclaiming).

Ideally, a sentence requires at least one subject and one verb. Sometimes the subject of a sentence can be hidden, but the verb must be visible and present in the sentence. Verb is called the heart of a sentence.  

Example:

Do it. (In this sentence, a subject ‘you’ is hidden but verb ‘do’ is visible)   

“[A sentence is] a group of words, usually containing a verb, that expresses a thought in the form of a statement, question, instruction, or exclamation and starts with a capital letter when written.”

In other words, a complete English sentence must have three characteristics:

• First, in written form, a sentence begins with a capital letter and ends with a period (i.e., a full stop) [.], a note of interrogation (i.e., a question mark) [?], or a note of exclamation (i.e., an exclamation mark) [!].
• Second, it must express a complete thought, not fragmented.  
• Third, it must contain at least one subject (hidden/visible) and one verb comprising an independent clause. (An independent clause contains an independent subject and verb and expresses a complete thought.)

Examples of Sentence:

• Robert was a good king.
• He had a great army.
• He wanted to bring peace to his kingdom.
• There were many others who wanted to become king.
• They started plotting against him.
• Their plots were failing because of some trusted friends of the king.
• Then they started killing those trusted friends.
• Eventually, they succeeded in their plan of killing the king.
• Did they make a good move?
• Can they find a new king without dispute?
• After the death of the king, everyone wanted to be a king.
• A great chaos broke out in the kingdom.
• People were anxious and unhappy.
• War does not bring anything good to the common people.
• It only brings sorrow and dismay.

Note: all these examples of sentence contain at least one verb and one subject and gives a complete sense.