A sentence is the basic unit of meaning in English. It expresses a complete thought—whether it’s a statement, a question, a command, or an exclamation. Every sentence follows a structure, and knowing how that structure works is essential for writing and speaking clearly.
In this guide, you’ll learn what a sentence is, the parts that make it complete, the different types of sentences used in English, and the common errors to avoid.
What is a Sentence?
In English, a sentence is a group of words that expresses a complete thought. It must include at least a subject and a predicate, and it should stand alone as a complete idea.
A sentence can be as short as one word or as long as several clauses, but it must be grammatically complete.
Examples:
- Short sentence: Birds fly.
- Longer sentence: When the storm passed, the sky turned bright, and a rainbow appeared.
If a group of words is missing a subject, a verb, or doesn’t make sense on its own, it isn’t a sentence—it’s a fragment.
Understanding what makes a sentence complete is the foundation of learning how to build better sentences in English.
Basic Components of a Sentence
To understand how sentences work, it helps to know the parts that make them complete. Every sentence includes at least a subject and a predicate, and many sentences also contain objects, complements, modifiers, and punctuation.
1. Subject
The subject tells us who or what the sentence is about. It’s usually a noun or pronoun.
- The students arrived early.
- My phone is missing.
2. Predicate
The predicate includes the verb and everything related to the action or state of being. It tells what the subject does or what condition it’s in.
- The students arrived early.
- My phone is missing.
3. Object
Objects receive the action of the verb.
- Direct object: She bought a notebook.
- Indirect object: He gave his sister a message.
4. Complement
Complements add information about the subject or object.
- Subject complement: The soup tastes salty.
- Object complement: They elected him president.
5. Modifiers
Modifiers give extra detail. They can be adjectives, adverbs, or phrases that describe other parts of the sentence.
- The tired runner collapsed quickly.
(“Tired” describes “runner,” and “quickly” describes “collapsed.”)
6. Conjunctions
Conjunctions connect words, phrases, or clauses. They help build compound and complex sentences.
- Coordinating: and, but, or
- Subordinating: because, although, if
- Correlative: either…or, not only…but also
7. Punctuation
Punctuation marks organize sentence elements and clarify meaning.
- Commas separate items or clauses.
- Semicolons connect closely related clauses.
- Periods show the end of a complete thought.
Knowing how these components work together helps you write stronger, clearer sentences in any context.
Types of Sentences by Function
Sentences in English can be grouped by their purpose or function. Each type serves a different role in communication—whether you’re stating something, asking a question, giving a command, or showing emotion.
1. Declarative Sentence
A declarative sentence makes a statement or shares information. It ends with a period.
- The meeting starts at 9 a.m.
- They live near the city center.
2. Interrogative Sentence
An interrogative sentence asks a question and ends with a question mark.
- Are you joining us later?
- What time does the movie start?
3. Imperative Sentence
An imperative sentence gives a command, instruction, or request. It can end with a period or an exclamation mark, depending on tone.
- Please close the door.
- Stop talking!
4. Exclamatory Sentence
An exclamatory sentence shows strong emotion or excitement. It always ends with an exclamation mark.
- What a beautiful sunset!
- I can’t believe we won!
These functional types help express tone and intent, and they appear in all kinds of writing—from academic to conversational.
Types of Sentences by Structure
Sentence structure refers to how clauses are combined within a sentence. In English, there are four main types based on structure. Each one adds variety and depth to writing.
1. Simple Sentence
A simple sentence has one independent clause. It may include modifiers or compound subjects/predicates, but it expresses a single complete thought.
- The lights flickered.
- Jack and Nina arrived early and saved seats.
2. Compound Sentence
A compound sentence has two or more independent clauses joined by a coordinating conjunction (like and, but, or so) or a semicolon.
- The food was cold, but we ate it anyway.
- She called me; I didn’t answer.
3. Complex Sentence
A complex sentence includes one independent clause and at least one dependent clause. It shows a relationship between ideas.
- Although it rained, they continued the game.
- She stayed until the meeting ended.
4. Compound-Complex Sentence
This structure contains at least two independent clauses and one or more dependent clauses.
- While I was preparing dinner, the kids finished their homework, and my partner set the table.
These structures give writers different tools for organizing ideas clearly and effectively, whether the goal is to explain, compare, or build on a point.
Common Sentence Errors
Even when you know the basics of sentence construction, it’s easy to make mistakes that affect clarity. Below are three of the most common sentence-level errors—and how to avoid them.
1. Run-on Sentences
A run-on sentence joins two or more complete thoughts without proper punctuation or conjunctions.
Incorrect: He got home late he didn’t explain why.
Correct: He got home late, but he didn’t explain why.
Run-ons often happen when writers try to connect related ideas without checking if each part can stand alone.
2. Comma Splices
This error happens when two independent clauses are joined with just a comma.
Incorrect: The wind picked up, the sky turned gray.
Correct: The wind picked up, and the sky turned gray.
Use a coordinating conjunction, semicolon, or separate the ideas into two sentences.
3. Sentence Fragments
A fragment is an incomplete sentence that’s missing a subject, verb, or full idea.
Incorrect: Because the signal wasn’t clear.
Correct: We missed the call because the signal wasn’t clear.
Fragments often appear when dependent clauses are left standing alone.
Recognizing and fixing these issues helps ensure your writing is both grammatically correct and easy to follow.
Enhancing Sentence Clarity
Writing clearly isn’t just about avoiding errors—it’s about making sure every sentence communicates the right message. These tools help refine sentence structure and improve readability.
1. Modifiers
Modifiers describe or give more detail about a word or phrase. They can be adjectives, adverbs, or modifying phrases.
- The exhausted student finished her assignment quickly.
(“Exhausted” modifies “student”; “quickly” modifies “finished.”)
Be careful with placement—misplaced or dangling modifiers can confuse the reader.
2. Conjunctions
Conjunctions connect words, phrases, or clauses and help establish relationships between ideas.
- Coordinating: and, but, or, so
- Subordinating: because, although, since
- Correlative: either…or, neither…nor
Using the right conjunction makes your sentence more logical and easier to understand.
3. Punctuation
Proper punctuation keeps sentence elements organized and prevents misreading.
- Commas separate items or clauses.
- Semicolons join related independent clauses.
- Colons introduce explanations or lists.
- Periods end complete thoughts.
A small punctuation mark can change meaning, so it’s worth reviewing how they’re used in different sentence types.
4. Sentence Variety
Mixing sentence lengths and structures makes writing more engaging and natural.
- Too many short sentences: The dog barked. The door opened. We looked outside.
- Improved: The dog barked as the door opened, and we looked outside to see what caused it.
Clear writing comes from choosing the right sentence structure and expressing ideas with precision.
FAQs
What defines a complete sentence in English?
A complete sentence has at least a subject and a verb, and it expresses a full idea. If it’s missing any of these elements, it may be a fragment.
How do sentence types differ by function and structure?
Function refers to the purpose of a sentence—whether it states something, asks a question, gives a command, or expresses emotion. Structure refers to how clauses are arranged: simple, compound, complex, or compound-complex.
What are common sentence errors and how can I avoid them?
Common errors include run-on sentences, comma splices, and fragments. To avoid them, check if your sentence contains a full thought, uses correct punctuation, and connects ideas clearly.
Why is sentence variety important in writing?
Using different sentence types and lengths helps maintain flow, avoid repetition, and keep the reader engaged. It also makes writing sound more natural and expressive.
How can I improve my sentence construction skills?
Practice identifying sentence parts and types, read examples, and revise your writing by checking for clarity and structure. Reading aloud can also help spot awkward or confusing sentences.