Compound Sentences
You already know how to join two simple sentences using conjunctions like and, but, or, and so. Now you will learn how to make your compound sentences longer and more interesting by expanding them with prepositional phrases and noun phrases.
What You'll Learn
- How to expand compound sentences by adding prepositional phrases
- How to expand compound sentences by adding noun phrases
- How to place phrases in the right position within a compound sentence
- How to use commas correctly in expanded compound sentences
When to Use
- Adding detail about where or when: "The children played at the playground, and their parents sat on the benches nearby."
- Describing nouns more fully: "The tall boy in the blue uniform kicked the ball, but the goalkeeper with the big gloves saved it."
- Giving extra information about how something happened: "She ran along the corridor, so the strict prefect at the door stopped her."
- Making your writing more vivid: "A group of noisy birds landed on the rooftop, and the old cat under the table woke up at once."
- Combining actions with details: "We waited at the bus stop for twenty minutes, but the bus from Tampines never arrived."
How to Form
Review: What Is a Compound Sentence?
A compound sentence joins two simple sentences (also called independent clauses) with a coordinating conjunction.
| Part | Example |
|---|---|
| Simple sentence 1 | The girl read a book. |
| Conjunction | , and |
| Simple sentence 2 | Her brother drew a picture. |
| Compound sentence | The girl read a book, and her brother drew a picture. |
Expanding with Prepositional Phrases
A prepositional phrase starts with a preposition and ends with a noun. It tells you where, when, or how.
| Preposition | Prepositional Phrase | What It Tells |
|---|---|---|
| at | at the hawker centre | where |
| on | on Saturday morning | when |
| with | with great excitement | how |
| in | in the school library | where |
| during | during the assembly | when |
| along | along the narrow path | where |
You can add prepositional phrases to either or both parts of a compound sentence:
| Original Compound Sentence | Expanded Version |
|---|---|
| She finished her homework, and she went out. | She finished her homework at her desk, and she went out to the playground. |
| He woke up early, but he was still late. | He woke up early on Monday morning, but he was still late for school. |
Expanding with Noun Phrases
A noun phrase is a noun with words that describe it (adjectives, articles, or other modifiers). It gives more detail about who or what.
| Simple Noun | Expanded Noun Phrase |
|---|---|
| the boy | the cheerful boy in my class |
| a dog | a small brown dog with floppy ears |
| the cake | the delicious chocolate cake on the table |
You can replace simple nouns with noun phrases to add detail:
| Original Compound Sentence | Expanded Version |
|---|---|
| The boy scored a goal, and the crowd cheered. | The tallest boy on the team scored a goal, and the excited crowd in the stands cheered. |
| A bird flew away, but the cat stayed. | A tiny bird with bright feathers flew away, but the lazy grey cat stayed. |
Key Rules
- Keep both independent clauses complete: Even after you add phrases, each clause must still have its own subject and verb. "The boy at the back ran, and the girl near the gate waited." -- both clauses can stand alone.
- Place the prepositional phrase close to the word it describes: "She ate a sandwich in the canteen" (tells where she ate). If you move it, the meaning may change: "She ate a sandwich in the canteen" could mean the sandwich was already in the canteen.
- Use a comma before the conjunction: When joining two complete clauses, place a comma before and, but, or, or so. "The students lined up**,** and the teacher led them to the hall."
- Do not overload a sentence: Adding one or two phrases per clause is enough. Too many phrases make the sentence confusing. Aim for clear and natural-sounding sentences.
- Match the phrase to the right noun or verb: A noun phrase expands a noun; a prepositional phrase usually tells where, when, or how about the verb or noun it follows. Make sure the reader can easily tell which word the phrase describes.
- Check subject-verb agreement after expanding: When you add words around the subject, do not lose track of agreement. "The basket of red apples on the counter was heavy" -- the subject is "basket" (singular), not "apples".
Common Mistakes
| Wrong | Right | Why |
|---|---|---|
| The boy at the field kicked the ball and the girl at the gate cheered. | The boy at the field kicked the ball**,** and the girl at the gate cheered. | A comma is needed before the conjunction when joining two complete clauses |
| She put the vase with flowers on the shelf beautiful. | She put the beautiful vase with flowers on the shelf. | Adjectives go before the noun, not after it |
| The students in the hall was excited, and the teachers was busy. | The students in the hall were excited, and the teachers were busy. | "Students" and "teachers" are plural -- use "were" |
| My mother cooked dinner at home delicious. | My mother cooked a delicious dinner at home. | The adjective must be placed before the noun inside the noun phrase |
| The cat on the roof, and the dog in the garden barked. | The cat sat on the roof, and the dog in the garden barked. | The first clause is missing a verb -- every clause needs a subject and a verb |
| He ran to the park with and she cycled to school with. | He ran to the park with his friends, and she cycled to school with her sister. | A preposition must be followed by a noun or noun phrase |
Clue Words
Prepositions that start prepositional phrases:
in, on, at, by, with, from, to, for, along, across, near, over, into, during, between, under, behind, beside, through
Words that signal noun phrases:
the, a, an, this, that, these, those, my, your, his, her, its, our, their
Adjectives often found in noun phrases:
big, small, tall, short, old, young, new, bright, dark, noisy, quiet, beautiful, delicious, cheerful, strict
Tip: To check if you have expanded your sentence well, try reading each clause on its own. If it still makes sense as a complete sentence with the extra phrases, you have done it correctly.
Practice Tips
- Start simple, then expand: Write a basic compound sentence first (e.g., "The boy ran, and the girl walked."). Then add a prepositional phrase or noun phrase to one clause at a time.
- Ask "where?", "when?", or "what kind?": After writing a sentence, ask yourself these questions. If you can answer them, add the detail as a phrase. "The boy ran" -- Where? "across the field." Now: "The boy ran across the field, and the girl walked."
- Underline the subject and verb: After expanding your sentence, underline the subject and verb in each clause. If a clause is missing either one, fix it.
- Read aloud for flow: Read your expanded sentence out loud. If it sounds too long or confusing, split it into two sentences or remove a phrase.
Quick Reference
| What to Do | How | Example |
|---|---|---|
| Add where/when/how detail | Insert a prepositional phrase | "She studied in the library, and he played at the field." |
| Describe a noun more fully | Use a noun phrase | "The kind old lady next door baked cookies, and the happy children ate them." |
| Join two expanded clauses | Use comma + conjunction | "The girl with the red bag sat down**,** and the boy beside her smiled." |
| Keep it clear | Limit to 1-2 phrases per clause | Avoid: "The tall boy in the big blue shirt from the school near the park ran quickly along the road." |