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.
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.
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.” - (Cambridge Advanced Learner’s Dictionary & Thesaurus © Cambridge University Press.)
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.)
Types of Sentences
Structurally, sentences are of four types:
- Simple sentence
- Compound sentence
- Complex sentence, and
- Compound-complex sentence.
A simple sentence must have a single clause (a single verb) which is independent, and it cannot take another clause.
I always wanted to become a writer. (One clause – one verb)
A compound sentence must have more than one independent clause with no dependent clauses. Some specific conjunctions, punctuation, or both are used to join together these clauses.
I always wanted to become a writer, and she wanted to become a doctor. (Two independent clauses – two verbs)
A complex sentence also has more than one clause but of one them must be an independent clause and the other/others must be (a) dependent clause(es). There are also some particular connectors for the clauses of a complex sentence to be connected.
I know that you always wanted to be a writer. (Here, a dependent clause is followed by a connector and an independent clause. The other way around is also possible.)
A compound-complex sentence (or complex–compound sentence) is a mixture of the features of compound and complex sentences in one sentence. So, it must contain at least two independent clauses and at least one dependent clause.
I know that you always wanted to become a writer, but I always wanted to become a doctor. (Here, one dependent clause is followed by a complex connector and two independent clauses with a compound conjunction between them.)
Functionally, sentences are of mainly four types:
- Declarative sentence
- Imperative sentence
- Interrogative sentence, and
- Exclamatory sentence
An assertive sentence (declarative sentence) simply expresses an opinion/feeling, or makes a statement, or describes things. In other words, it declares something. This type of sentence ends with a period (i.e., a full-stop).
- I want to be a good cricketer. (a statement)
- I am very happy today. (a feeling)
We use an imperative sentence to make a request or to give a command. Imperative sentences usually end with a period (i.e., a full stop), but under certain circumstances, it can end with a note of exclamation (i.e., exclamation mark).
- Please sit down.
- I need you to sit down now!
An interrogative sentence asks a question. Interrogative sentences must end with a note of interrogation (i.e., question mark)
- When are you going to submit your assignment?
- Do you know him?
An exclamatory sentence expresses the overflow of emotions. These emotions can be of happiness, wonder, sorrow, anger, etc.
- What a day it was!
- I cannot believe he would do that!
Source: Learn Grammar