The Sentence

Lesson 5: Types of Sentences by Function

Lesson: 5 of 9 | Level: 🔵 Beginner

1. Lesson Overview

Every sentence in English does something. It makes a statement, asks a question, gives an instruction, or expresses a strong feeling. These four communicative purposes define the four functional types of sentences in English — declarative, interrogative, imperative, and exclamatory.

While the previous lesson examined sentence structure — how many clauses a sentence contains and how they relate to one another — this lesson examines sentence function — what a sentence is designed to do. The two systems are independent of each other. A declarative sentence, for instance, can be simple, compound, complex, or compound-complex. Function and structure are separate dimensions of the same sentence.

Understanding sentence function matters both for reading and for writing. It helps you interpret what a sentence is asking of you and choose the right form when you write.

Objectives

By the end of this lesson, you will be able to:

• Define and identify declarative, interrogative, imperative, and exclamatory sentences
• Understand how each sentence type is formed and punctuated
• Use all four sentence types accurately in writing
• Recognise and correct common errors related to sentence function

2. Core Content

A. Declarative Sentences

A declarative sentence makes a statement. It conveys information, expresses an opinion, or describes a fact. It is the most common sentence type in English and is used in virtually every form of written and spoken communication.

A declarative sentence ends with a full stop and follows the standard word order of subject + verb + (additional elements).

For example:

The Earth is the third planet from the Sun and the only known planet to support life. Charles Darwin published On the Origin of Species in 1859 after more than twenty years of careful research.

In both sentences, a statement is being made — a fact is presented and information is conveyed. The first describes the Earth; the second states a historical fact about Darwin. Both end with a full stop and follow standard word order.

Declarative sentences can be affirmative or negative.

B. Interrogative Sentences

An interrogative sentence asks a question. It ends with a question mark and typically involves a change in word order — the auxiliary verb moves before the subject, or a question word introduces the sentence.

There are four main types of interrogative sentences in English.

Yes/no questions

Yes/no questions can be answered with “yes“ or “no“. They are formed by placing an auxiliary verb before the subject.

For example:

Has the glacier retreated significantly this year? Do coral reefs recover quickly from bleaching events?

In the first sentence, the auxiliary verb precedes the subject, the glacier. In the second, do precedes coral reefs. Both can be answered with yes or no.

Wh- questions

Wh- questions ask for specific information and begin with a question word — who, what, where, when, why, which, or how.

For example:

Where is the deepest point on Earth located? How many species of deep-sea fish have been discovered so far?

In the first sentence, where asks about the location. In the second, how many asks about the quantity. Both require a specific answer rather than a simple yes or no.

Tag questions

Tag questions are short questions added to the end of a declarative sentence to seek confirmation or agreement. If the main clause is affirmative, the tag is negative; if the main clause is negative, the tag is affirmative.

For example:

The Amazon is the world’s largest river by discharge, isn’t it? Antarctica has no permanent human population, does it?

In the first sentence, the affirmative main clause the Amazon is the world’s largest river is followed by the negative tag isn’t it? In the second, the negative main clause is followed by the affirmative tag does it?

Indirect questions

An indirect question is a question embedded within a declarative sentence or another question. It follows standard word order — subject + verb — rather than inverted word order.

For example:

Scientists are still debating whether life exists elsewhere in the universe. Do you know how deep the Mariana Trench is?

In the first sentence, whether life exists elsewhere in the universe is an indirect question embedded within a declarative sentence. In the second, how deep the Mariana Trench is is an indirect question embedded within a direct question. Note that in both cases, the subject precedes the verb — there is no inversion.

C. Imperative Sentences

An imperative sentence gives a command, an instruction, a request, or a piece of advice. The subject of an imperative sentence is always you — but it is not stated; it is understood.

Imperative sentences end with a full stop or, when the command is forceful or urgent, an exclamation mark.

For example:

Record the temperature readings at hourly intervals. Never underestimate the importance of peer review in scientific research.

In the first sentence, the instruction is directed at a specific person or group — the understood subject is you. In the second, never adds emphasis to the instruction. Neither sentence states its subject explicitly.

Imperative sentences can be made more polite by adding please at the beginning or end.

Imperative sentences can also use let’s to include the speaker in the instruction.

For example:

Let’s examine the data before drawing any conclusions. Let’s consider the environmental impact of deep-sea mining.

In both sentences, let’s — a contraction of let us — invites the reader or listener to join in the action, making the instruction collaborative rather than directed.

D. Exclamatory Sentences

An exclamatory sentence expresses a strong emotion — surprise, admiration, delight, shock, or indignation. It ends with an exclamation mark and is typically introduced by what or how.

For example:

What an extraordinary diversity of life the coral reef supports! How rapidly the glaciers of Greenland are retreating!

In the first sentence, what introduces a noun phrase — an extraordinary diversity of life — followed by the subject and verb — the coral reef supports. In the second, how introduces an adjective — rapidly — followed by the subject and verb — the glaciers of Greenland are retreating.

The structure of exclamatory sentences introduced by what and how follows a fixed pattern.

For example:

What a significant contribution Marie Curie made to the understanding of radioactivity! How little we know about the deep ocean, despite decades of exploration!

In the first sentence, what a significant contribution introduces a noun phrase before the subject and verb. In the second, how little introduces an adverb phrase expressing the degree of our ignorance.

3. Usage in Context

4. Common Errors and Corrections

5. Lesson Mastery

After completing this lesson, you should now be able to:

    ✅ Define and identify declarative, interrogative, imperative, and exclamatory sentences

    ✅ Understand how each sentence type is formed and punctuated

    ✅ Use all four sentence types accurately in writing

    ✅ Recognise and correct common errors related to sentence function