First, a bit of grammar so we are all singing from the same song sheet!
Conjunction are words used to join two words or, more likely, groups of words, together.
There are three categories of conjunction.
- Coordinating: and, but, for, nor, or, so, yet
- Correlative: either/or, neither/nor, whether/or
- Subordinating: after, after, although, as, as if, as long as, because, before, even if, even though, if, if only, in order that, now that, once, rather than, since, so that, than, that, though, till, unless, until, when, whenever, where, whereas, wherever, while
Coordinating conjunctions link parts of speech of equal weight.
- Two words: The cockney slang for ‘stairs’ is ‘apples and pears‘.
- Two phrases: On the second day of Christmas, my true love gave to me: two turtle doves and a partridge in a pear tree.
- Two clauses: You take the high road and I’ll take the low road.
Correlative conjunctions come in pairs.
- Either/or: Either you pass the exam or you won’t be able to go to college.
- Neither/nor: Neither your father nor your mother are prepared to support this petition.
- Whether/or: Whether you like it or not, it’s time to go home.
Subordinating conjunctions link two clauses, when one clause is dependent on the other.
- Jane felt ill after eating so much treacle tart.
- After eating so much treacle tart, Jane felt ill.
Notice the comma after the dependent clause; if you choose to present a ‘weak’ clause at the start of the sentence, it needs a comma.
The issue is whether or not there should be a comma before a coordinating conjunction.
YES when …
- The conjunction joins two sentences (which are then called ‘independent clauses’!).
We’ve booked for lunch at the Pizza Express, and we are planning on taking a walk afterwards.
- The conjunction expresses a contrast.
I’ll eat anything, but she is lactose intolerant.
- The conjunction is for the last item in a list. This calls for the Oxford comma, or serial comma.
My favourite ice cream flavours are chocolate, coffee, and honeycombe.
NO when …
- The conjunction joins two short sentences (even though they are ‘independent clauses’!).
You take the high road and I’ll take the low road.
- You have a pair of commas, around an aside, coming up: I am tired so, when I get a minute, I’ll take a nap.
- In a list, it’s unambiguous: I took three A levels: Maths, Physics and Chemistry.
If in doubt, you might prefer to leave the comma out. A misplaced comma is worse than no comma at all – in most cases!