Both coordinating conjunction and subordinating conjunction join clauses. Both belong to the same part of speech – conjunction. Both are positionally fixed at the beginning of their clauses.
But the two are different in many ways.
Conjunctive adverbs, coordinating conjunctions, and subordinating conjunctions link clauses, and hence they’re often termed linkers. Learn the difference between other two pairs of linkers:
1. Coordinating conjunction joins two independent clauses; subordinating conjunction joins a dependent clause to an independent clause.
A coordinating conjunction joins two independent clauses. Examples:
I wanted to go for a walk, but it started raining.
He missed the bus, so he took a taxi to work.
A subordinating conjunction introduces an adverb clause and joins it to an independent clause. Examples:
When the movie ended, everyone applauded.
Since he moved to the city, he’s made many new friends.
2. They’re punctuated differently.
When a coordinating conjunction joins two independent clauses, it is usually preceded by a comma. When it joins phrases though, it is usually not accompanied by a comma. Examples:
I wanted to go for a walk, but it started raining.
He finished his report early, so he decided to take a long lunch break.
My parents and my sister are coming to visit this weekend. [No comma to join phrases]
When an adverb clause comes before the independent clause, a comma always separates the two:
When the movie ended, everyone applauded.
Since he moved to the city, he’s made many new friends.
When an adverb clause comes after the independent clause, a comma is generally not used. A comma is used when there is contrast between the two clauses:
Everyone applauded when the movie ended.
He’s made many new friends since he moved to the city.
3. Clause containing subordinating conjunction is not sequentially locked; the other is.
But for few exceptions, an adverb clause can occupy initial or end position. In other words, it’s not sequentially locked. Example:
You will pass the exam if you study hard.
If you study hard, you will pass the exam.
The independent clause that follows coordinating conjunction can’t switch place with the first independent clause. Example:
We could take a road trip, or we could fly to our destination.
Or we could fly to our destination, we could take a road trip. [Incorrect]
4. Coordinating conjunction can join words, phrases, or dependent clauses; subordinating conjunction can’t.
Coordinating conjunctions can join units smaller than independent clause: They can join words, phrases, or dependent clauses. A conjunctive adverb though can’t join units other than independent clauses. Examples:
My parents and my sister are coming to visit this weekend.
We can watch a movie or a TV show tonight.
If it rains tomorrow or if the weather is too windy, we’ll postpone the picnic.
5. Coordinating conjunction can express only limited relationships; subordinating conjunction, many.
Subordinating conjunctions far outnumber coordinating conjunctions, enabling them to express far more relationships. (Although we recognize seven coordinating conjunctions – FANBOYS – strictly speaking there are just three – ABO.)
