Types of Sentences: 4 by Purpose and 4 by Structure

There are four types of sentences by purpose and four by structure. By purpose, a sentence is declarative (a statement), interrogative (a question), imperative (a command or request) or exclamatory (a statement of strong feeling). By structure, it is simple, compound, complex or compound-complex, depending on how many clauses it has and what kind they are.

When a lesson or quiz asks for "the 4 types of sentences," it usually means the four purpose types; the Del Mar College Stone Writing Center, for example, lists exactly those four. The structure types are a second set of four, which is why you will also see "eight types" quoted.

The two sets do not compete. Every sentence gets one label from each, so "When the bell rings, put your pens down." is imperative by purpose and complex by structure.

The 4 types of sentences by purpose

Purpose, also called function, is the job a sentence does: it tells, asks, commands or exclaims. The end punctuation is a strong clue, but the job decides the type.

Declarative sentences: statements

A declarative sentence makes a statement. It gives a fact, an opinion or an explanation, and it ends with a period. Del Mar College's writing center calls it the most common sentence in writing.

• It is sunny today.
• That film was far too long.
• She works from home on Fridays.

Interrogative sentences: questions

An interrogative sentence asks a question and ends with a question mark. Some questions put a verb such as can, did or is before the subject and expect a yes-or-no answer. Others open with a question word: who, what, when, where, why or how.

• Where are my keys?
• Did you eat lunch?
• Can she come with us?

Imperative sentences: commands and requests

An imperative sentence tells someone to do something. It can be an order, an instruction, a piece of advice or a polite request. The subject is usually not written, but it is understood to be "you": "(You) close the door." Most imperatives end with a period. An urgent command can end with an exclamation mark and still be imperative. As GrammarBook's guide to exclamatory sentences puts it, "If a sentence includes a command, it is not exclamatory: It is imperative."

• Close the door.
• Please send me the report by Friday.
• Do not touch the wet paint.
• Watch out for that car!

Exclamatory sentences: strong feeling

An exclamatory sentence makes a statement with strong feeling, such as surprise, joy, fear or anger, and ends with an exclamation mark. Use them sparingly in formal writing; they are more at home in dialogue, stories and personal posts.

• I cannot believe we won!
• What a long day it has been!
• The cake is burning!

Greetings such as "Happy birthday!" look exclamatory, but GrammarBook treats them as shortened commands ("Have a happy birthday!"), so they are not good examples of the type.

The 4 types of sentences by structure

Structure depends on clauses. A clause is a group of words with its own subject and verb. An independent clause can stand alone as a sentence. A dependent clause cannot: as the University of Nevada, Reno Writing & Speaking Center puts it, "A dependent clause cannot stand alone even if it contains a subject and a verb." It usually starts with a word such as because, although, when, if, who, which or that.

The Purdue OWL's page on sentence types sorts sentences by counting those two kinds of clause, and the four definitions below follow it.

Simple sentences

A simple sentence has one independent clause and no dependent clause. It can still be long. Two subjects joined by "and," or two verbs sharing one subject, still make one clause, so the sentence stays simple.

• The baby is sleeping.
• Tom and his sister play football on Saturdays.
• She finished her essay and emailed it to her teacher.

Compound sentences

A compound sentence has two or more independent clauses and no dependent clause. The clauses are joined by a comma and a coordinating conjunction (and, but, for, or, nor, so, yet), or by a semicolon. A semicolon can also come before a conjunctive adverb, a linking word such as however or therefore, as the Purdue OWL's guide to commas and semicolons explains. The sentence is still compound.

• I was tired, but I kept working.
• She likes tea, and he prefers coffee.
• The shop was closed; the bakery next door was open.
• The bus was late; however, we still made it to class.

Complex sentences

A complex sentence has one independent clause and at least one dependent clause. The dependent clause can come first, last or in the middle.

• Although it was late, she kept reading.
• Because it was raining, we stayed inside.
• We will start when everyone arrives.
• The student who sits by the window asked a question.

Many words that open a dependent clause, such as because, although and since, are also common ways to begin a sentence. Our list of sentence starters groups them by the job they do, with an example for each.

Compound-complex sentences

A compound-complex sentence has two or more independent clauses and at least one dependent clause. It needs at least three clauses, so save it for ideas that have several connected parts.

• While I cooked dinner, the kids watched TV, and my partner cleaned the house.
• I wanted to call you, but I lost my phone, which had your number in it.
• If it rains tomorrow, we will play indoors, but the coach still wants everyone there at ten.

How to tell them apart in 10 seconds

Ask two questions about any sentence: what job does it do, and how many clauses does it have?

Purpose: check the job, then the punctuation

1. Does it ask for an answer and end with a question mark? It is interrogative.
2. Does it tell someone to do something, usually with no written subject? It is imperative, even if it ends with an exclamation mark.
3. Does it state something with strong feeling and end with an exclamation mark? It is exclamatory.
4. Does it simply state something and end with a period? It is declarative.

Structure: count the clauses

1. Find each subject-and-verb group that could stand alone as a sentence. Those are the independent clauses.
2. Look for a clause that opens with a word such as because, although, when, if, who, which or that and cannot stand alone. That is a dependent clause.
3. Match the two counts to the table below.

Four traps to avoid

• "And" does not always mean compound. "Tom and his sister play football" has two subjects but one clause, so it is simple. The UNR Writing & Speaking Center lists "The dog and the fox jumped over the cat." as a simple sentence for the same reason.
• "However" does not make a sentence complex. When it means "on the other hand," however is a conjunctive adverb, not a word that opens a dependent clause. "She loves summer. However, she hates the heat." is two simple sentences, and "She loves summer; however, she hates the heat." is one compound sentence. For the punctuation, see whether you can start a sentence with however.
• An exclamation mark does not make a command exclamatory. "Watch out for that car!" gives an order, so it is imperative.
• A reported question is a statement. "She asked where the station was." and "I wonder where my keys are." are declarative and end with a period. Idaho State University's handout on questions and question marks says such combinations "are statements, so they always end with periods, not question marks."

Using sentence types in your own writing

Most of the sentences you write will be declarative, so structure is where most of your variety will come from. The Purdue OWL's strategies for sentence variation warn that "Too many sentences with the same structure and length can grow monotonous for readers." A run of simple sentences can feel choppy, and a run of compound-complex ones can be hard to follow. Mixing them, and saving the longest structures for ideas that need them, keeps a paragraph easy to read.

The same thinking works at paragraph level. A topic sentence states a paragraph's main point, so it is usually declarative, whichever type of paragraph you are writing, from descriptive to persuasive. If you want a draft to work on, the paragraph generator writes a first version from a topic; rewrite a few of its sentences in a different structure and compare how they read. Before you hand in the final version, a pass through the grammar checker is a quick way to look for slips you may have introduced while rewriting.