Types of Sentences by Function: What you need to Know

Sentences are the largest grammatical units on the grammatical rank scale above the clause. The grammatical rank scale is a ranking of elements of structure from the lowest, being the morpheme, to the highest—the sentence. As the highest element of structure on the grammatical rank scale, sentences are classified based on the roles or functions they perform. The additional qualities associated with sentences is what forms the functional classification of sentences. Classification of sentences by function include the following;

1. Declarative Sentence

2. Imperative Sentence

3. Interrogative Sentence

Declarative sentences

Declarative sentences are sentences that state facts. They are sentences also known as statements. Declarative sentences are used in defining concepts, providing answers to questions, telling stories, habitual behaviours, and making factual statements—statements that are considered true beyond reasonable doubt. Examples of declarative sentences include;

1. John is always attentive when lectures are going on.

2. Many scientists have argued that the earth is round.

3. I drink water and exercise every morning.

4. Students must take their studies seriously to become useful to society.

5. What God cannot do does not exist.

Imperative sentences

Imperative sentences are sentences that are generally used to issue  commands. They are also known as directives as they are used to direct and influence actions. Imperative sentences can be used to demand a response from an audience, the truth from a criminal, a polite instruction to an elderly person, etc. Imperative sentences have their subjects elipted—that is, the subjects of imperative sentences are not included in their formation but can be determined from the context of the exchange that necessitate the command. They may be harsh or polite depending on the context and punctuation used. Examples of imperative sentences include;

1. Go and get me some groceries from the grocery store down the street.

2. Let the poor boy have some breathing space, please.

3. Bring your assignments over here for assistance now.

4. Don't tell me what to do young man!

5. Stop getting on my nerves, Mr. Plankton!

A good point to note about imperative sentences is that they always start with a verb, usually an action verb.

Interrogative sentences

Interrogative sentences are sentences that are used to request information from persons. They refer to sentences that demand answers from an interlocutor. There are some criteria for the classification of interrogative sentences namely; Polar interrogatives, and Non-polar interrogative sentences.

Polar interrogative

Polar interrogative sentences are sentences that are used to demand Yes or No answers. Put another way, they are questions whose answers come in the format of a simple Yes or No. For example;

1. Are you a boy?

2. Will you be late to work?

3. Can you drive a car?

4. Does she have a bachelor's degree?

5. Will you attend the fathers meeting?

You will notice that each polar question starts with an auxiliary verb, and this is because polar questions are formed by a transformational process known as Auxiliary—NP(subject) inversion, where the subject of a sentence switches position with the auxiliary verb to form a question.

Non-polar interrogatives

Non-polar interrogatives are questions that do not demand a Yes or No answer, unlike polar questions. They are grouped into three, namely; WH-questions, Tag questions, and Rhetorical questions.

WH-questions

WH-questions are simply questions that begin with the WH-words for example; who, why, how, what, where, when, etc. These are basically interrogative pronouns and they are used to introduce questions without a Yes or No answer. For example;

1. Who are you?

2. Where are you?

3. What are you doing over there?

4. Why did you come here by this time of the night?

5. When did you come back from United States?

Tag questions

Tag questions are statements that end with question tags. They are Non-polar interrogatives that start off as declarative sentences and end as questions. For example;

1. We are going to the beach, aren't we?

2. You will take care of the bills, won't you?

3. You are not planning to leave us, are you?

4. They don't have anymore food left, do they?

5. She can't fight the cancer anymore, can she?

Tag questions are usually a mix of auxiliary verbs and negation—negative adverb "not" through a process known as contraction. This applies only when the declarative part of the sentence is a positive proposition. But if the declarative part of the sentence is a negative proposition, then the tag is positive— an auxiliary verb without a contracted negation ('nt).

Rhetorical questions

Rhetorical questions are questions which by their nature do not require an answer. These are questions asked to send people into deep reflections, to ponder over a topic or phenomena, or to lay emphasis on a point. For example;

1. Why do human beings exist?

2. Why does man go through all these struggles just to die in the end?

3. What is the purpose of living when you will eventually die?

4. When will life become fair?

5. Why do good people suffer?

Related posts:

• Types of Sentences by Structure
• Grammatical Rank Scale Explained 
• What are Sentences