These excerpts are taken from an excellent resource for NZ writers: Style Book, A guide for New Zealand writers and editors Derek Wallace and Janet Hughes.
Comma
The main purpose of the comma (,) is to separate and define parts of a sentence, especially where two words or parts coming together could lead to misunderstanding, as in the following examples.
In the sea below, the rocks looked very small.
In 1998, 50 people at the camping ground at any one time had been considered a lot.
Where no confusion is likely, however, contemporary open style favours omission of the comma. (Note that it is the placing of the adverbial clause before the main clause that makes the comma necessary. If the order were reversed, a comma is not needed.)
Although he had never eaten octopus before, he enjoyed it.
He enjoyed the octopus although he had never eaten it before.
Where two or more adjectives precede and qualify a noun, commas are generally used to separate them.
Dominic Jones considered the coroner to be a loyal, devoted, and affectionate friend.
However, where the adjectives in question regularly occur in a particular time-honoured order, the comma is conventionally omitted.
An ugly little parrot sat in a cage on top of the filing cabinet.
In some instances, particularly where there are no more than two adjectives, an open style of punctuation would omit the comma whether or not the adjectives have a customary order.
The body had been lying in a damp cold room.
When two or more phrases, words, letters or figures precede an and, or, or nor, a comma is often required to avoid ambiguity.
The long day of intense heat, the night of heavy drinking, and inadequate food may have impaired his judgement.
When and joins just two words or phrases, the comma is omitted.
Dominic Jones considered the coroner to be a loyal and devoted friend.
A comma should usually precede the conjunction and when it divides two parts of a compound sentence.
The coroner examines the corpse, and the police officer watches closely.
There is potential for ambiguity if the comma is omitted. However, when verbs in a compound sentence have a common subject, the comma is usually not needed.
She was expecting broken bones and was astonished that there were none.
Commas can be used parenthetically, i.e. to insert a phrase or clause into a sentence.
The search, if it was to have any chance of success, would require a great many people.
If a clause adds information but may be omitted without seriously changing the meaning of the sentence, then it is usually separated by commas.
The searchers, who are fully equipped, will push on.
The use of a comma after abbreviations such as e.g. and i.e. is rapidly disappearing in published writing. However, it is helpful to punctuate before, and where applicable after, the material introduced by these abbreviations in order to acknowledge the break in continuity. For example:
Certain facts, e.g. the man's identity, the nature of his death and subsequent disappearance, and the identity of the woman who bought his drinks, remain unexplained.
A comma is the standard form of punctuation before a short direct quotation following an introductory phrase.
She said, "I will not do it".
The comma is used in numbers to separate hundreds, thousands, hundreds of thousands, and millions.
Ungrammatical Practices
The use of a comma between a verb and its subject.
Those who supported the police, agreed that the most important task was to recover the body.
The writer of such a sentence has either been confused by the unusual length of the subject group, or has anticipated a potential difficulty for the reader who, without the comma, might focus on a more familiar order of words: the police agreed. Perhaps the best solution is to rewrite the sentence:
Police supporters agreed that the most important task was to recover the body.
The non-provision of commas to enclose an absolute phrase.
Then darkness having fallen the searchers returned to the camp.
This should be written as:
Then, darkness having fallen, the searchers returned to the camp.
The omission of a second comma when alternatives occur.
By the time the purpose of the search had been announced, many, if not most of the personnel had been selected.
A comma after "most" is conventionally inserted.
By the time the purpose of the search had been announced, many, if not most, of the personnel had been selected.
Colon
The main functions of the colon (:)are:
- To introduce an explanation of preceding statements.
The police are stumped: the man was carrying no identification and had pitched his tent without registering at the office. They have searched the man's tent, combed the path between the hotel and the camping ground, even scaled the cliff face in case anything had lodged in rocks or bushes: all to no avail.
- To introduce a list.
The man's pockets contained the following articles:
- an empty brown vinyl wallet
- a Swiss army knife
- a stopwatch.
- To introduce a question.
One further matter remains outstanding: who was that masked man?
- To introduce a quotation of more than a few words.
The officer in charge of the investigation, Detective Inspector Charley Pierce, said: "We have not yet given up hope of identifying the man. We are extending our inquiries to neighbouring towns."
- To go between two numerals to express a ratio, such as the scale of a map.
The other item was a 1:1,000,000 scale topographical map.
Semicolon
The semicolon (;) is a halfway house between the comma and the full stop. In many instances, it could be replaced by either of these, but it signals a certain degree of relatedness between statements: closer than would necessitate separate sentences, but not so close that a comma would suffice to distinguish them.
The wine with its full body and rich taste inevitably exercised its influence; the cooking drew on all the skills of a long Italian tradition; and in the face of this gastronomic invasion the diners abandoned their strategising and gave themselves wholly to the meal.
The semicolon is frequently used in parallel constructions (statements which have the same form) and in sentences where ideas are contrasted. The two effects often occur together.
His speech was excellent; his manners were appalling.
The semicolon is also used between items in a series, or in lists, where commas alone would not suffice to separate the components.
By the end of the evening the dates on the wine bottles could scarcely be distinguished: 1990; 1989; 1988 or 1983?
