Writing · Free lesson
Join sentences with and, but and so
A connecting word does more than join sentences. It shows the relationship between your ideas.
Professor Scott MendozaThe short answer
Use “and” to add, “but” to show a contrast, and “so” to introduce a result. When these words join two complete clauses, a comma usually comes before the connecting word.
Decide how the ideas relate.
First decide whether you are adding information, showing a contrast, or explaining a result. Then check both parts. A complete clause has a subject and a verb and can stand alone as a sentence: “The café was full” is one example. In this lesson, join two complete clauses with a comma followed by “and,” “but” or “so.” The connector tells the reader how the second idea relates to the first.
Let the connection do some work.
I wanted to go for a walk. It was raining.
I wanted to go for a walk, but it was raining.
“But” highlights the contrast between the plan and the weather. A comma comes before “but” here because it joins two complete clauses.
Three useful connections
Add with “and”
I made lunch, and Sam set the table.
Contrast with “but”
I called, but no one answered.
Show a result with “so”
It was late, so we went home.
Try it now
Choose the connection you mean.
Read all answers and explanations
Show a contrast: “I wanted to stay, ___ I had to leave.”
but“But” highlights the contrast between wanting to stay and needing to leave.
Show the result: “The last train had left, ___ we took a taxi.”
so“So” explicitly makes taking a taxi the result of missing the train. “And” can connect the events, but it does not state the result relationship as directly.
Simply add another activity: “I washed the dishes, ___ Lee dried them.”
and“And” adds Lee’s activity to yours. No contrast or cause-and-result meaning is needed here.
Put it into practice
Join the ideas. Show the connection.
Choose a connecting word and the punctuation before it. Watch your sentence take shape, then check it.
Sentence 1 of 2
The café was full.
We found another place.
Your goal: Make finding another place the explicit result of the full café.
See a model answer
The café was full, so we found another place.
“So” introduces the result. Here we use a comma before “so” to join two complete clauses in one sentence.
I wanted to stay, but I had to leave.
“But” highlights the contrast. The comma separates the two complete clauses joined by “but.”
Choose the relationship first. In these examples, a comma comes before the connector, and the second clause continues in the same sentence.
A little more clarity
Common questions
A few useful details before you move on.
Do I need a comma before every “and”?
No. The pattern in this lesson joins two complete clauses. When “and” joins two actions with one shared subject, you usually do not need a comma.
“I opened the window and turned off the fan.” Compare: “I opened the window, and Sam turned off the fan.”
Can “and” and “so” both work in the same sentence?
Sometimes. “And” can simply connect two events; “so” explicitly presents the second as a result. Choose the word that matches what you want to show. Our exercises ask for a particular relationship.
“The shop was closed, and we went home” connects the events. “The shop was closed, so we went home” explains why we went home.
Can I join two complete sentences with just a comma?
In standard written English, a comma alone usually cannot join two complete clauses. That error is called a comma splice. For this lesson, either add a suitable connector or use a full stop to make two sentences.
“I was tired, I went home” → “I was tired, so I went home.”
Take it into your day
Find two related ideas in something you have written. Choose a connection that makes their relationship clear.
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