Compound Sentences: How to Join Ideas Clearly and Correctly
At some point, every student starts writing sentences that feel… stuck. Choppy. Short. Like they’re afraid to talk to each other. That’s usually the moment I introduce compound sentences.
Compound sentences help students connect ideas that belong together — without creating run-ons or comma disasters. Once students understand how they work, their writing immediately becomes smoother, clearer, and more confident.
This lesson walks students through the rules of compound sentences, gives them guided practice, and then lets them apply the skill independently.
What Are Compound Sentences?
Definition
A compound sentence is made up of two independent clauses.
Each independent clause can stand alone as a complete sentence.
The clauses are joined in a specific, rule-based way.
Rule 1: Independent Clauses
Each side of a compound sentence must be a complete thought.
If one side cannot stand alone, it is not a compound sentence.
Example:
✔ I wanted to go outside, and it started to rain.
✘ I wanted to go outside, and because it started to rain.
Rule 2: Coordinating Conjunctions (FANBOYS)
Most compound sentences are joined using a comma + coordinating conjunction.
The coordinating conjunctions are remembered with FANBOYS:
For
And
Nor
But
Or
Yet
So
Structure:
Independent Clause + comma + FANBOYS + Independent Clause
Example:
I finished my homework, but I forgot to hand it in.
Rule 3: Semicolons (Advanced Option)
Compound sentences can also be joined using a semicolon if the ideas are closely related.
Structure:
Independent Clause ; Independent Clause
Example:
The bell rang; the class stayed silent.
Common Mistakes to Watch For
Using a comma without a conjunction (comma splice)
Joining a dependent clause by mistake
Forgetting the comma before FANBOYS
Practice Together
Work through these examples as a class.
I wanted to sleep in, ___ I set my alarm early.
The test was difficult, ___ everyone finished on time.
We can walk to school, ___ we can take the bus.
The movie was long, ___ it never felt boring.
She studied all night, ___ she felt confident the next day.
Class Discussion Prompts
Are both sides complete sentences?
Which FANBOYS makes the most sense?
Would a semicolon work here instead?
Practice Together — Answer Key
I wanted to sleep in, but I set my alarm early.
The test was difficult, yet everyone finished on time.
We can walk to school, or we can take the bus.
The movie was long, but it never felt boring.
She studied all night, so she felt confident the next day.
Practice Alone (Student Worksheet)
Instructions
Combine each pair of independent clauses to form a compound sentence.
Use a comma and a coordinating conjunction (FANBOYS).
Conclusion
Compound sentences are one of those grammar tools that pay off immediately. Students stop stacking short sentences, their writing flows better, and their ideas sound more connected and intentional.
