What Is a Sentence? (Subject and Predicate): English Grammar Guide

A sentence is the foundation of written and spoken English. It expresses a complete thought, allowing us to communicate ideas clearly and effectively. Understanding what makes a sentence complete—and how the subject and predicate work together—is one of the first steps to mastering English grammar.

In this guide, we’ll explore what a sentence is, how it is structured, the difference between subjects and predicates, the main types of sentences, and common mistakes to avoid.

What Is a Sentence?

A sentence is a group of words that expresses a complete idea or thought. It always contains at least two main parts:

1. Subject – who or what the sentence is about.

2. Predicate – what is said about the subject, usually containing a verb.

For example:

• Maria sings beautifully.

  • Maria = subject

  • sings beautifully = predicate

Even in its simplest form, a sentence must have these two elements to make sense.

The Subject: The “Who” or “What” of the Sentence

The subject is the part of the sentence that tells us who or what performs the action or is being described.

1. Simple Subject

The simple subject is the main noun or pronoun.

• Example: Dogs bark loudly.

  • “Dogs” is the simple subject.

2. Complete Subject

The complete subject includes all the words that describe the main noun.

• Example: The big brown dogs bark loudly.

  • “The big brown dogs” is the complete subject.

3. Compound Subject

Sometimes, a sentence has more than one subject performing the action.

• Example: John and Lisa are studying English.

  • “John and Lisa” are both subjects.

4. Implied Subject

In commands or requests, the subject is often understood as “you.”

• Example: Sit down!

  • The subject “(You)” is implied.

The Predicate: The “Action” or “Description”

The predicate tells what the subject does or what happens to it. It always contains a verb, which is the action or state of being.

1. Simple Predicate

The simple predicate is the main verb.

• Example: She writes.

2. Complete Predicate

The complete predicate includes the verb and all words that describe the action or give more information.

• Example: She writes in her journal every morning.

3. Compound Predicate

A sentence can also have two or more actions performed by the same subject.

• Example: She writes and draws in her journal.

Examples of Subject and Predicate

Here are some examples showing how the subject and predicate work together:

Types of Sentences

English sentences come in several types, depending on their purpose and structure.

1. Declarative Sentence

• Purpose: Makes a statement or gives information.

• Example: I love learning English.

2. Interrogative Sentence

• Purpose: Asks a question.

• Example: Do you like grammar lessons?

3. Imperative Sentence

• Purpose: Gives a command or request.

• Example: Please turn off the light.

4. Exclamatory Sentence

• Purpose: Expresses strong emotion.

• Example: What a beautiful sunset!

Sentence Structures

Apart from the sentence types, English also categorizes sentences by their grammatical structure.

1. Simple Sentence

Contains one independent clause (one subject and one predicate).

• Example: The baby is sleeping.

2. Compound Sentence

Has two or more independent clauses joined by a conjunction (such as and, but, or).

• Example: The baby is sleeping, and the mother is cooking.

3. Complex Sentence

Contains one independent clause and one or more dependent clauses.

• Example: The baby is sleeping because she is tired.

4. Compound-Complex Sentence

Has at least two independent clauses and one or more dependent clauses.

• Example: The baby is sleeping, and the mother is cooking while the father works outside.

Understanding Clauses and Phrases

A clause is a group of words with a subject and a predicate.

• Independent clause: Can stand alone as a sentence.

• Dependent clause: Cannot stand alone; it depends on the main clause for meaning.

A phrase, on the other hand, lacks either a subject or a predicate and cannot stand alone.

• Example of a phrase: In the morning

• Example of a clause: She wakes up early.

Common Sentence Errors

Understanding sentence structure helps avoid common grammar mistakes.

1. Sentence Fragment

A group of words that lacks a subject, predicate, or complete thought.

• Incorrect: Because I was tired.

• Correct: I went to bed early because I was tired.

2. Run-On Sentence

Two or more independent clauses joined incorrectly.

• Incorrect: I love English it is my favorite subject.

• Correct: I love English because it is my favorite subject.
  or
  I love English. It is my favorite subject.

3. Subject-Verb Disagreement

The subject and verb must agree in number.

• Incorrect: She go to school every day.

• Correct: She goes to school every day.

4. Missing Predicate or Subject

• Incorrect: Running fast. (no subject)

• Incorrect: The boy. (no predicate)

• Correct: The boy is running fast.

Why Sentence Structure Matters

Good sentence structure improves clarity, flow, and readability. Whether you’re writing an essay, an email, or speaking in English, forming complete and varied sentences makes your communication more effective.

Understanding subjects and predicates helps you:

• Avoid sentence fragments and run-ons

• Improve writing rhythm

• Construct complex ideas clearly

• Strengthen both spoken and written English

Practice Tips

1. Identify subjects and predicates in everything you read.

   • Example: “The sun rises in the east.”

     • Subject: The sun

     • Predicate: rises in the east

2. Combine simple sentences using conjunctions.

   • Example: “I study every morning.” + “I take a break at noon.”
     → “I study every morning, and I take a break at noon.”

3. Vary your sentence structure when writing essays or stories.

   • Mix short and long sentences to make your writing engaging.

4. Double-check for complete thoughts.

   • If your sentence doesn’t make sense on its own, add the missing part.

Final Thoughts

A sentence is more than just a group of words—it’s the building block of communication. By mastering the subject (who or what the sentence is about) and the predicate (what happens or what is said about the subject), you can create clear, meaningful, and grammatically correct English sentences.

The key is balance: every sentence should express a complete thought, connect smoothly to others, and accurately reflect what you want to say. With consistent practice, recognizing subjects and predicates will become second nature, helping you write and speak English with confidence and precision.

FAQs

What is a sentence in plain terms?

A sentence is a group of words that expresses a complete thought. At minimum, it includes a subject (who or what the sentence is about) and a predicate (what the subject does or is). For example, “Birds sing” is a complete sentence: Birds is the subject, and sing is the predicate. Without either part, the idea feels unfinished and the sentence becomes a fragment.

What exactly are the subject and predicate?

The subject names the person, place, thing, or idea the sentence describes. The predicate tells something about the subject—usually an action or a state of being—and must contain a verb. In “The students studied quietly,” the students is the subject, and studied quietly is the predicate. If you can ask “Who/what is this sentence about?” and then “What is said about them?”, you’ll find both parts reliably.

What is the difference between simple and complete subject/predicate?

The simple subject is just the main noun or pronoun (e.g., Maria). The complete subject includes the simple subject plus modifiers (e.g., My talented friend Maria). Likewise, the simple predicate is the main verb or verb phrase (e.g., has been practicing), while the complete predicate includes everything that follows the verb and adds meaning (e.g., has been practicing the piano every morning).

Can a sentence have more than one subject or more than one predicate?

Yes. A compound subject joins two or more subjects with a conjunction: “Sam and Priya present today.” A compound predicate gives the same subject multiple actions: “Priya presents and answers questions.” You can also combine both: “Sam and Priya present and answer questions.” Be sure the verb agrees with the subject as a whole.

How do imperative sentences handle the subject?

In imperatives (commands and requests), the subject is usually implied as “you,” even when not written. “Close the window” really means “(You) close the window.” Because the subject is understood, the sentence is still complete: the predicate is the verb phrase, and the subject is you, implied.

What is a sentence fragment, and how can I fix it?

A fragment lacks a subject, a predicate, or a complete thought. Example: “Because the weather was bad.” To fix it, add the missing part: “We stayed indoors because the weather was bad.” Fragments often start with subordinating conjunctions (because, although, when) or are just phrases lacking a true verb (e.g., “Running fast down the hall”). Add a subject-verb unit and connect it to a main clause.

What is a run-on sentence and how do I correct it?

A run-on incorrectly joins two independent clauses. Example: “I love grammar it helps me write clearly.” Fix it by:

• Using a period: “I love grammar. It helps me write clearly.”
• Using a semicolon: “I love grammar; it helps me write clearly.”
• Using a comma plus a coordinating conjunction: “I love grammar, because it helps me write clearly.”

How do I tell the difference between a clause and a phrase?

A clause has both a subject and a predicate; it can be independent (stand alone) or dependent (needs an independent clause to complete the thought). A phrase lacks either a subject or a predicate and cannot stand alone. “When the bell rang” is a dependent clause; “after lunch” is a prepositional phrase. Always check for a subject-verb pair to spot a clause.

How do questions and inverted sentences affect the subject and predicate?

In questions, the normal order often flips, but the parts remain. “Are the lights on?” has the subject the lights and the predicate are on. In sentences starting with here or there (expletives), the true subject follows the verb: “There are two options.” Identify the real subject by finding the noun the verb agrees with.

How does subject–verb agreement work with tricky subjects?

Match the verb to the real subject’s number. Collective nouns can be singular or plural depending on meaning: “The team is winning” (as a single unit) vs. “The team are arguing among themselves” (members acting individually). With compound subjects joined by and, use a plural verb (“Bread and butter are on the table”). With or/nor, the verb agrees with the nearest subject (“Neither the teacher nor the students are ready”).

Can non-nouns be subjects?

Yes. Gerunds (verbs ending in -ing used as nouns) and infinitives (to + verb) can act as subjects: “Reading improves vocabulary.” “To practice daily builds skill.” Treat these as singular unless joined into a compound subject (e.g., “Reading and writing are essential”).

What are linking verbs, and how do they affect the predicate?

Linking verbs (be, seem, become, appear, feel, look, sound, taste) connect the subject to a subject complement—a noun, pronoun, or adjective that renames or describes the subject. “The soup smells delicious.” The predicate provides information about the subject’s state rather than an action on an object.

How can I quickly identify the subject and predicate in real sentences?

Use a two-step test: (1) Ask “Who or what is this about?”—that’s your subject. (2) Ask “What is being said about that subject?”—that’s your predicate. Strip out introductory phrases, clauses, and modifiers. In “After the meeting, the senior manager approved the plan,” the subject is the senior manager; the predicate is approved the plan.

What types of sentences (by purpose) should I know?

There are four: declarative (statements), interrogative (questions), imperative (commands/requests), and exclamatory (strong emotion). Regardless of type, each must include a subject and a predicate (with “you” implied in imperatives).

How do simple, compound, complex, and compound-complex sentences differ?

A simple sentence has one independent clause (The baby is sleeping.). A compound sentence joins two or more independent clauses (The baby is sleeping, and the mother is cooking.). A complex sentence combines one independent clause with at least one dependent clause (The baby is sleeping because she is tired.). A compound-complex sentence has at least two independent clauses and at least one dependent clause.

What punctuation helps separate subjects and predicates—or clauses—clearly?

Within a clause, the subject and predicate aren’t separated by special punctuation; word order does the work. Between clauses, use commas with coordinating conjunctions (for, and, nor, but, or, yet, so), semicolons to connect closely related independent clauses, and periods to end a thought. Avoid comma splices (a comma joining two independents without a conjunction).

How do I avoid the most common sentence errors?

Watch for three issues: fragments (add a missing subject/verb or attach to a main clause), run-ons (separate or correctly join clauses), and agreement mistakes (ensure the verb matches the real subject). Read aloud to hear completeness and rhythm; if you pause naturally where a period should go, you may have a run-on.

Do adverbials and introductory elements change the core sentence?

No. Adverbial phrases and clauses add context (time, place, reason, condition) but do not replace the subject–predicate core. In “When the bell rings, students pack their bags,” the main clause is students pack their bags. The introductory dependent clause (When the bell rings) sets timing but can’t stand alone.

What about sentences beginning with “there is/there are” or “it is”?

These are expletive constructions that postpone the real subject. In “There are many reasons to study,” the true subject is many reasons. In “It is important to rest,” the real subject is the infinitive phrase to rest (or the delayed subject clause). Ensure your verb agrees with the delayed subject, not with there or it.

How can I practice identifying subjects and predicates effectively?

Try three drills: (1) Underline subjects once and predicates twice in short texts; (2) Convert fragments into full sentences by adding the missing part; (3) Combine short, choppy sentences into compound or complex forms. Over time, you’ll internalize the patterns and write more clearly and confidently.

Can you give a quick checklist to test sentence completeness?

• Subject found? (Who/what is this about?)
• Predicate present? (Verb shows action or state?)
• Complete thought? (Can it stand alone?)
• Correct connection? (Clauses joined with proper punctuation and conjunctions?)
• Agreement? (Subject and verb match in number and person?)

If you can check all five boxes, you likely have a clear, correct sentence with a solid subject–predicate core.

English Grammar Guide: Complete Rules, Examples, and Tips for All Levels