Semi-colons and colons

Many people get muddled over the usage of colons (:) and semi-colons (;).

In simple terms, a colon is an introducer. It points forward and introduces:

• a list (as above)
• an extended quotation or sometimes direct speech. Mr Jones says: “I’m delighted by this promotion. . .”
• an explanation or amplification of the preceding part of the sentence. There was only one thing to do: run.

The last use is the one most people struggle with. Basically, a colon is a rather dramatic punctuation mark: it makes the reader pause and theatrically announces something to come which will add new information to the part of the sentence before the colon. Usually, the part of the sentence before the colon is a complete sentence in itself, and the colon could be replaced with words like namely, that is, for example, for instance, because and therefore.

The semi-colon is a little like a comma but with special powers. It has two main jobs:

• It can join two separate sentences that are closely related. It was his first job as a salesman; before this, he had been a teacher.
• It can help divide up long and complicated lists that may otherwise be confusing. I ordered a prawn cocktail, not with salad; a steak, chips and peas; an ice cream sundae without nuts; and a pitcher of beer.

Correct usage of both colons and semi-colons is important for good, accurate writing. These days, some writers view them as old-fashioned and abandon them altogether, littering the page with dashes and comma splices instead. If you want to be taken seriously in any form of communication, I advise sticking with the rules of English grammar.

Common mistakes in writing

They rear their ugly heads daily as I proofread and edit, worming their way into document after document as if sticking a tongue out at me goading, Catch me if you can. And I do catch them, day after day - mistakes I find so often they jump out at me from the page as if 3D.

Here's my top five:

1. Comma splices: It's amazing how many writers join two sentences together with a comma, and rather alarming how prevalent this has become in published books (take a look at this weekend's HP finale).
2. Missing/incorrect apostrophes: Did you notice the apostrophe in weekend's above? Many seem to feel the apostrophe is either optional, or something to plonk anywhere in the vicinity of the word in question.
3. Random capitals: I spend an impressive amount of my day decapitalising words.
4. Inconsistent styling: It's thirteen miles to London, but three lines later it's 15 days until Christmas.
5. Spellchecked nonsense: Just because that word is spelled correctly, doesn't mean it's the right word. This morning I found the following while proofreading a serious article on a church: The chap is a plaice for queer time (The chapel is a place for quiet time).