This section will explain a little about what conjunctions are and how they should be used. Conjunctions are words or phrases that are used to join two independent clauses together.
Coordinating conjunctions are and/or/but/nor/as/for/so. When they are used to connect two independent clauses together they should be accompanied by a comma, which comes before the coordinating conjunction.
Some writers would argue that the comma itself is an adequate separation and would omit the comma in sentences where the two clauses are short and balanced. If in any doubt, I would use a comma as doing so cannot be wrong in this situation.
AND Of all the coordinating conjunctions, 'and' is the most common and the one where the use or otherwise of the comma is possibly most troublesome. The comma is needed if the 'and' is used to connect two independent clauses.
Paul went to Kenya for his holiday, and Steve went to Dorset.
Jim's mother washed the floor, and his dad just sat in front of the fire.
If, however it is used simply to connect two elements in the same clause or sentence, no comma is required.
Paul and Steve went to sunny Barrow in Furness on holiday this year.
He liked listening to rap and classical music.
BUT But requires a comma when acting as a coordinating conjunction, connecting two independent clauses.
The weather was fine on Sunday, but we chose to stay in and watch TV.
Jim's wife was a fine cook, but her pastry always tasted like clay.
When used to connect two ideas with the idea of 'with the exception of', no comma is needed.
Everybody but Jim got a new pencil.
It seemed like cake was given to everyone but me.
OR Again, a comma is required when or is used to separate two independent clauses.
I can cook something special tonight, or Jim can zoom down to the fish and chip shop.
Sharon can get you a ticket to the concert, or Suzie could take you to that new fish and chip shop.
If it is used to separate two elements in the same sentence, no comma is needed.
You can have fish or chicken.
Paul decided he wasn't that keen on Kenya or Dorset.
SUBORDINATING CONJUNCTIONS As well as the coordinating conjunctions noted and explained above, there is a whole raft of subordinating conjunctions. Some of them are:
Using these will make one of the two clauses in a sentence dependent on (or subordinate to) the other (main) clause. When these are used to separate two clauses (a main clause and a dependent or subordinate clause), no comma is needed:
The cyclist fell off her bike because the road was icy.
You cannot have any chocolate crumble unless you finish your main course.
However, if the dependent (or subordinate clause) is put first in the sentence, it must be offset with a comma.
Because the road was icy, the cyclist fell off her bike.
Unless you finish your main course, you cannot have any chocolate crumble.
HOWEVER Here might be a good place to mention the word 'however'. Two independent clauses can be connected by coordinating conjunctions (with a comma) but cannot be connected by the word however. Using the word 'however' to connect two independent clauses is a common mistake.
Paul decided to go to Kenya, and Steve went to Dorset. (Correct)
Paul decided to go to Kenya, but Steve went to Dorset. (Correct)
Paul decided to go to Kenya, however Steve went to Dorset. (Incorrect)
In the example above, it would be better to make the two clauses into separate sentences.
Paul decided to go to Kenya. Steve, however, went to Dorset.
You can use 'however' to express contrast. It is usually offset with a comma.
There was, however, no chance of any cricket being played on Wednesday.
She, however, was a truly awful cook.
My culinary skills are, however, second to none.
Test your understanding of conjunctions with this exercise.