7.15 The Comma, Co-ordinate elements

Elements of equal rank or relation in a sentence are said to be co-ordinate. The co-ordinate elements may be words or phrases in a series, or they may be entire clauses.

(a) Nouns and noun phrases

Items in a series may be separated by commas:

• Complacency, urbanity, sentimentality, whimsicality

They may also be linked by co-ordinating conjunctions such as and or or:

• economists, sociologists or political scientists
• the good, the bad and the ugly

Opinions differ on whether and when a comma should be inserted before the final and or or in a sequence. In keeping with the general trend toward less punctuation, the final comma is best omitted where clarity permits, unless there is a need to emphasize the last element in the series. This comma is usually omitted in the names of firms and always before an ampersand:

• Deeble, Froom & Associates Ltd.
• Cohen, Hansen and Larose

On the other hand, it is usually inserted if the items in the series are phrases or clauses of some length, or if omission of the comma might lead to ambiguity or misunderstanding:

• Tenders were submitted by Domicile Developments Inc., East End Construction, Krista, and Ryan and Scheper.

A comma is also required before etc.:

• He brought in the wine, the glasses, etc.

A more complex situation occurs when apposition commas are used together with co-ordinating commas, as illustrated below:

• Carla Tavares, a recent MBA graduate, three students and a technician set up the experiment.

The sentence should be rephrased so that no non-restrictive appositive occurs within a co-ordinate element:

• A recent MBA graduate named Carla Tavares, three students and a technician set up the experiment.

Alternatively, semicolons may be used to separate elements in a complex series (see also 7.23 The Semicolon, Co-ordinate elements):

• Jane Stewart, MP for Brandt, Ont.; Stan Keyes, MP for Hamilton West, Ont.; John Nunziata, MP for York-South Weston . . .

(b) Clauses

A comma is normally used to separate two main clauses in a compound sentence when they are joined by a co-ordinating conjunction (and, but, or, nor, yet or for):

• They are often called individualists, and in economic matters they were, but in social matters, the dominating concept was that of good neighbourliness.
  —M. M. Fahrni

If the clauses are short or closely related, the commas may be omitted before and, but, or or nor:

• He opened the letter and then he read the contents.
• Life is short but art is long.

Co-ordinate clauses not joined by a co-ordinating conjunction are usually separated by a heavier mark of punctuation than the comma:

• When the white men came we had the land and they had the Bibles; now they have the land and we have the Bibles.
  —Chief Dan George

A comma will suffice, however, if the clauses are short, or if the writer wishes to emphasize a contrast or lead the reader on to the following clause as quickly as possible:

• There are good regulations, there are bad regulations.
• It was not the duration of the pilot project that caused concern, it was the size of the project team.

When a number of independent co-ordinate clauses follow one another, a comma should be used after each one except (usually) the last, in accordance with the rule for items in a series (see 7.15 The Comma, Co-ordinate elements(a)):

• She investigated the matter, wrote a report, presented it to the committee and answered everyone’s questions satisfactorily.

It is a common error to confuse a simple sentence having a compound predicate with a compound sentence requiring a comma between clauses. Note the difference between the following examples:

• She investigated the matter and then wrote a detailed report.
  (simple sentence)
• She investigated the matter, and then the committee began its work.
  (compound sentence)

Where the clauses of a compound sentence are joined by a conjunctive adverb (such as however, instead, meanwhile, otherwise, similarly, so, still, then, therefore or yet), a semicolon is usually called for, though a comma will often suffice before so, then and yet:

• Much of English-speaking Canada has been populated . . . by a highly literate people, drawn in part from the educated classes of the Old Country, yet in its two hundred years of existence it has produced few books and not a single great one.
  —E. A. McCourt

(c) Adjectives

A series of adjectives modifying a noun may or may not be co-ordinate. The adjectives are co-ordinate if their order does not affect the meaning, in which case they should be separated by a comma. If they are not co-ordinate, that is, if one adjective modifies the phrase formed by the following adjective(s) plus the noun, then they should not be separated by a comma:

• a rich, creamy sauce

but

• a naive domestic burgundy

Adjectives of both types may of course occur together:

• a tender, succulent young chicken

The rule stated above, however, is not an infallible guide. When in doubt omit the comma, as in:

• The plain honest truth is that he is a liar.

The final adjective in the series should not be separated from the following noun by a comma:

• Nations require strong, fair, open, decisive government.

(d) Antithetic expressions

Antithetic expressions are usually separated by a comma:

• This proposal is not to be tossed lightly aside, but to be hurled with great force.

However, short expressions of this type may not require a comma:

• The more wit the less courage.

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