Compound Sentences

Simple explanation

A compound sentence joins two simple sentences (two complete thoughts) using a coordinating conjunction — and, but, or, so, yet, for, nor.

Both halves of a compound sentence are equal — neither depends on the other. Either could stand alone as its own sentence.

Why it matters

Compound sentences make your speech and writing flow naturally. Without them, every thought sits in its own short sentence — choppy and disconnected. With them, you show the relationship between ideas: contrast, addition, choice, or result.

How to form a compound sentence

Simple sentence 1 + comma + conjunction + Simple sentence 2

Simple 1	Conjunction	Simple 2	Full compound sentence
I was tired	but	I kept working	I was tired, but I kept working.
She called me	and	I answered	She called me, and I answered.
You can email	or	you can call	You can email, or you can call.
It rained all day	so	we stayed inside	It rained all day, so we stayed inside.

The comma rule — this is where most people go wrong

When joining two complete sentences with a conjunction, place a comma before the conjunction.

Each conjunction has its own meaning

Conjunction	What it shows	Example
and	addition — both things are true	She is smart, and she works hard.
but	contrast — one thing surprises or contradicts	He studied hard, but he failed.
or	choice — one or the other	Call me, or send a message.
so	result — the second follows from the first	I was hungry, so I ordered food.
yet	contrast (more formal than but)	She was tired, yet she kept going.

Wrong vs right

Daily life usage

1. "The project was challenging, but the team delivered it on time."
2. "You can attend in person, or you can join the call online."
3. "She spoke clearly, and everyone understood her point."
4. "The traffic was terrible, so I reached late."
5. "He wanted to leave early, yet he stayed until the work was done."

Practice quiz

Quick summary

• A compound sentence joins two complete thoughts with and, but, or, so, yet, for, nor.
• Always put a comma before the conjunction when both halves are complete sentences.
• Choose the right conjunction — each one shows a different relationship between the ideas.