Chapter 20: What is a Sentence?

Understanding what is a sentence forms the foundation of all written and spoken communication in English. A sentence is more than just a collection of words—it’s a complete thought that stands on its own and makes perfect sense to the reader or listener. Every piece of writing you encounter, from simple text messages to complex novels, is built from sentences. Once you master the basics of sentence structure, you’ll have the power to express any idea clearly and confidently, whether you’re writing an email, telling a story, or having a conversation.

1. What is a Sentence?

A sentence is a group of words that expresses a complete thought. It’s the basic unit of communication in English, serving as the foundation for everything we write and say. Think of a sentence as a package that delivers a complete message to your reader or listener—it tells who or what you’re talking about and what’s happening, being done, or existing.

Here are 30+ examples of complete sentences that demonstrate what makes a sentence work:

Simple statements about everyday life:

• The sun shines.
• Birds fly south.
• Children play games.
• Water flows downhill.
• Dogs bark loudly.
• Cats sleep peacefully.
• Flowers bloom beautifully.
• Rain falls gently.
• Stars twinkle brightly.
• Wind blows strongly.

Sentences about people:

• My mother cooks dinner.
• The teacher explains lessons.
• Students study hard.
• Doctors help patients.
• Athletes train daily.
• Artists create paintings.
• Musicians play instruments.
• Writers tell stories.

Sentences describing states of being:

• I am happy.
• She is tired.
• They are friends.
• The book is interesting.
• The weather is cold.
• Life is beautiful.
• Time is precious.
• Knowledge is power.

Sentences about actions in different times:

• I walked to school.
• She will visit tomorrow.
• We eat breakfast every morning.
• He studied last night.
• They travel frequently.
• You understand the concept.
• The train arrives at noon.
• The store closes at nine.

Notice that each of these examples stands alone as a complete thought. You don’t need any additional information to understand what’s being communicated. This completeness is what distinguishes a sentence from a fragment or an incomplete thought.

2. Complete Thoughts: The Heart of Every Sentence

I. What Makes a Thought Complete?

A complete thought answers the basic questions a reader or listener would naturally have: Who or what are you talking about? What about them? A thought is complete when it doesn’t leave you wondering “and then what?” or “what about it?”

Consider these key characteristics of complete thoughts:

i. Self-sufficiency:

A complete thought stands on its own without needing additional information. When you read it, you don’t feel like something is missing.

• Complete: “The cat jumped.” (We know who did what)
• Incomplete: “The cat that” (We’re left wondering: the cat that what?)
• Complete: “Summer vacation begins tomorrow.” (Clear, complete information)
• Incomplete: “When summer vacation” (Missing the action or conclusion)

ii. Clarity of meaning:

A complete thought conveys a clear message that the reader can understand immediately.

• Complete: “The store sells fresh bread.” (Clear message)
• Incomplete: “Fresh bread at the store” (Is this a location? An observation? A wish?)
• Complete: “I finished my homework early.” (Definite statement)
• Incomplete: “Finishing my homework” (Action without context)

iii. Grammatical independence:

A complete thought can stand alone grammatically without relying on surrounding sentences for its meaning.

• Complete: “The concert was amazing.” (Stands alone perfectly)
• Incomplete: “Because the concert was” (Leaves us waiting for more)
• Complete: “Everyone applauded enthusiastically.” (Complete action)
• Incomplete: “Everyone who was there” (Who or what about them?)

II. Incomplete vs. Complete Thoughts

Understanding the difference between incomplete and complete thoughts is crucial for writing effective sentences. Let’s examine 30+ pairs to see this distinction clearly:

Common incomplete thoughts and their corrections:

More examples showing the transformation from incomplete to complete:

• Incomplete: “During the summer months”
  
  Complete: “During the summer months, we visit the beach frequently.”
• Incomplete: “The students in our class”
  
  Complete: “The students in our class work hard every day.”
• Incomplete: “Hoping for good weather”
  
  Complete: “We are hoping for good weather tomorrow.”
• Incomplete: “The package that arrived”
  
  Complete: “The package that arrived contains new books.”
• Incomplete: “Around the corner from my house”
  
  Complete: “Around the corner from my house stands an old library.”
• Incomplete: “Laughing at the joke”
  
  Complete: “Everyone was laughing at the joke.”
• Incomplete: “Since last Tuesday”
  
  Complete: “Since last Tuesday, the weather has been perfect.”
• Incomplete: “The tallest building”
  
  Complete: “The tallest building dominates the skyline.”
• Incomplete: “To finish the project”
  
  Complete: “To finish the project, we need more time.”
• Incomplete: “Whenever I visit”
  
  Complete: “Whenever I visit, my grandmother bakes cookies.”

3. The Two Essential Elements of a Sentence

Every sentence, no matter how simple or complex, must contain two essential elements: a subject and a verb. These two components work together to create meaning and form the backbone of sentence structure.

I. The Subject: Who or What

The subject tells you who or what the sentence is about. It answers the question “Who?” or “What?” is performing the action or being described. Without a subject, we don’t know what the sentence is discussing.

Subjects can be:

i. A single noun:

• Dogs bark.
• Rain falls.
• Sarah studies.
• Mountains rise.
• Time passes.
• Music plays.
• Flowers bloom.
• Stars shine.

ii. A pronoun:

• I run.
• She sings.
• They dance.
• We learn.
• He teaches.
• You understand.
• It works.

iii. A noun with descriptive words:

• The happy child laughs.
• My best friend helps.
• The old oak tree stands tall.
• Three tiny kittens play.
• The famous author writes novels.
• Every student participates.
• The bright morning sun warms the earth.

II. The Verb: The Action or State

The verb tells you what the subject does or what state the subject is in. It’s the engine of the sentence, providing the action or describing the condition of the subject.

Action verbs show what the subject does:

• Birds fly.
• The teacher explains the lesson.
• Children play outside.
• The athlete runs quickly.
• We study every evening.
• The wind blows fiercely.
• She writes stories.
• They dance beautifully.
• The phone rings constantly.
• Stars twinkle at night.

Being verbs (forms of “be”) describe states or conditions:

• I am happy.
• She is a doctor.
• They are friends.
• The book is interesting.
• We are students.
• He was tired yesterday.
• The answers were correct.
• You are kind.
• The weather is perfect.
• The children are excited.

III. Subject + Verb = Simple Sentence

When you combine a subject with a verb, you create a simple sentence—the most basic complete thought in English. Even though these sentences are short, they express complete ideas because they have both essential elements.

The simplest sentences (two words):

• Birds fly.
• Dogs bark.
• Cats meow.
• Babies cry.
• Fish swim.
• Bells ring.
• Lions roar.
• Horses gallop.
• Frogs jump.
• Eagles soar.
• Wolves howl.
• Snakes slither.
• Bees buzz.
• Crickets chirp.
• Thunder rumbles.

Simple sentences with being verbs:

• I am.
• She is.
• They are.
• We were.
• He was.
• You are.
• It is.

Slightly expanded simple sentences:

• The sun rises.
• Children laugh.
• Water flows.
• Time passes.
• Hearts beat.
• Clocks tick.
• Leaves fall.
• Snow melts.
• Fires burn.
• Grass grows.

These examples demonstrate that even the shortest sentences can be complete and meaningful when they contain both a subject and a verb. You can add more words to make sentences longer and more descriptive, but you always need these two essential elements.

4. Capital Letters and End Punctuation

Beyond having a subject and verb, every proper sentence must follow two important formatting rules: it must begin with a capital letter and end with appropriate punctuation. These conventions signal to readers where sentences begin and end, making written communication clear and easy to follow.

I. Always Start with a Capital Letter

The first word of every sentence must begin with a capital letter. This rule applies regardless of what word starts the sentence—whether it’s a noun, pronoun, verb, adjective, or any other part of speech.

Examples showing proper capitalization:

• The sun rises in the east.
• Everyone loves summer vacation.
• Birds migrate south for winter.
• Many students study in the library.
• Quiet mornings are peaceful.
• Yesterday was a beautiful day.
• We enjoy reading books.
• Dancing requires practice and dedication.
• After dinner, we watch movies.
• Slowly, the snow began to fall.

Common words that must be capitalized at the start of sentences:

II. Always End with Proper Punctuation

Every sentence must end with one of three punctuation marks, depending on the type of sentence you’re writing:

i. Period (.) for statements:

Use a period to end sentences that make statements or give commands.

• The library closes at eight o’clock.
• My favorite color is blue.
• Please close the door.
• Turn left at the next corner.
• The meeting starts at noon.
• Summer vacation begins tomorrow.
• She studies mathematics at the university.
• The store sells fresh vegetables.
• Walk carefully on the icy sidewalk.
• Remember to bring your homework.

ii. Question mark (?) for questions:

Use a question mark to end sentences that ask questions.

• What time does the movie start?
• Where did you put my keys?
• How do you solve this problem?
• Why is the sky blue?
• Who wrote this book?
• When will you arrive?
• Can you help me with this project?
• Is it going to rain today?
• Have you finished your homework?
• Would you like some coffee?

iii. Exclamation mark (!) for strong emotions:

Use an exclamation mark to end sentences that express strong feelings, excitement, surprise, or urgency.

• What a beautiful sunset!
• Watch out for that car!
• I can’t believe we won!
• Happy birthday!
• This is amazing!
• Help!
• Stop right there!
• Wow, that was incredible!
• I’m so excited!
• Don’t touch that!

Complete sentences showing all three punctuation marks:

• The concert begins at seven. (statement)
• What time does the concert begin? (question)
• The concert was amazing! (exclamation)

• My sister graduated from college. (statement)
• Did your sister graduate from college? (question)
• Congratulations on your graduation! (exclamation)

• The package arrived this morning. (statement)
• Has the package arrived yet? (question)
• The package is finally here! (exclamation)

5. Identifying Sentences in Everyday Writing

Now that you understand what makes a sentence complete, you can practice identifying sentences in real writing. This skill helps you recognize proper sentence structure when you’re reading and avoid common errors when you’re writing.

Complete sentences (notice each has a subject and verb):

• The alarm clock rang loudly. (Subject: The alarm clock / Verb: rang)
• My younger brother plays soccer every Saturday. (Subject: My younger brother / Verb: plays)
• The delicious smell of fresh bread filled the kitchen. (Subject: The delicious smell of fresh bread / Verb: filled)
• Students from all grades participated in the science fair. (Subject: Students from all grades / Verb: participated)
• The ancient oak tree provides shade in summer. (Subject: The ancient oak tree / Verb: provides)
• Everyone enjoyed the surprise party. (Subject: Everyone / Verb: enjoyed)
• The first day of school always brings excitement. (Subject: The first day of school / Verb: brings)
• My grandmother tells wonderful stories about her childhood. (Subject: My grandmother / Verb: tells)
• The museum exhibits artwork from different centuries. (Subject: The museum / Verb: exhibits)
• Bright yellow sunflowers grow along the fence. (Subject: Bright yellow sunflowers / Verb: grow)

Not sentences (missing subject, verb, or both):

• Running through the park. (Missing subject: Who is running?)
• The big red balloon. (Missing verb: What about the balloon?)
• After the storm ended. (Incomplete thought: What happened after?)
• In the middle of winter. (Missing both: Who/what? What about it?)
• Because she was late. (Incomplete: What was the result?)
• The students studying in the library. (Missing helping verb: “are” studying)
• Whenever it rains. (Incomplete: What happens when it rains?)
• The book on the highest shelf. (Missing verb: What about the book?)

Practice identifying sentences in paragraph form:

Which of these are complete sentences?

1. The movie started at exactly seven o’clock. ✓ (Complete)
2. Eating popcorn and watching previews. ✗ (Incomplete—missing subject and helping verb)
3. Everyone laughed at the funny scenes. ✓ (Complete)
4. After the movie ended. ✗ (Incomplete—what happened after?)
5. We discussed our favorite parts. ✓ (Complete)
6. The main character who saved the day. ✗ (Incomplete—missing verb telling what the character did)
7. Tomorrow we might watch another film. ✓ (Complete)

6. Building Your First Sentences

Understanding sentence structure means you can now create your own sentences with confidence. Let’s practice building sentences from the ground up, starting with the simplest forms and gradually adding more detail.

Step 1: Choose your subject (who or what you’re talking about)

• Examples: dogs, children, the teacher, my friend, I, she, they

Step 2: Add a verb (what they do or are)

• Examples: run, sing, is, are, teach, laugh, think

Step 3: Make sure it’s a complete thought

• Subject + Verb = Complete sentence

Building from simple to more detailed:

Level 1 – Basic subject + verb:

• Dogs bark.
• Children play.
• The teacher teaches.
• I study.
• She reads.

Level 2 – Add when, where, or how:

• Dogs bark loudly.
• Children play outside.
• The teacher teaches every day.
• I study in the library.
• She reads before bedtime.

Level 3 – Add descriptive details:

• The neighbor’s dogs bark loudly at night.
• Happy children play outside after school.
• The experienced teacher teaches with enthusiasm every day.
• I study mathematics and science in the library.
• She reads adventure novels before bedtime.

Practice building your own sentences:

Use these sentence starters and complete them:

1. The sun _______________.
2. My family _______________.
3. Every morning _______________.
4. The beautiful flowers _______________.
5. After school _______________.
6. In winter _______________.
7. My best friend _______________.
8. During summer vacation _______________.
9. The old library _______________.
10. Every weekend _______________.

Sample completions:

1. The sun shines brightly in the morning.
2. My family enjoys eating dinner together.
3. Every morning I walk my dog around the neighborhood.
4. The beautiful flowers bloom in the garden throughout spring.
5. After school students participate in various clubs and activities.
6. In winter snow covers the entire landscape.
7. My best friend helps me with difficult homework assignments.
8. During summer vacation we travel to different countries.
9. The old library contains thousands of classic books.
10. Every weekend my grandmother bakes delicious cookies for us.

Exercises

Test Your Knowledge

Frequently Asked Questions

Conclusion

Understanding what is a sentence is the cornerstone of all effective communication in English. You now know that every complete sentence must have two essential elements—a subject (who or what) and a verb (action or state)—combined to express a complete thought. When you write, remember to always start with a capital letter and end with the appropriate punctuation mark, whether it’s a period for statements, a question mark for questions, or an exclamation mark for strong emotions.

As you continue your grammar journey, you’ll discover that mastering what is a sentence opens doors to more complex sentence structures and sophisticated writing techniques. Practice building sentences every day, starting with simple two-word combinations and gradually adding more details to make your thoughts clearer and more interesting. The ability to recognize and write complete sentences will serve you in every aspect of communication, from casual text messages to formal academic papers.

Keep practicing the skills you’ve learned in this chapter, and remember that every expert writer started exactly where you are now—with the fundamental building block of communication: the sentence. With consistent practice and attention to the basic rules, you’ll soon find yourself constructing sentences confidently and naturally.

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