Let’s face it. Unless you are an English teacher or a grammarian, you probably don’t think too much about comas, colons, and semicolons. Many people hesitate to insert advanced punctuation into their writing, because they feel uncomfortable with the “rules” that accompany their use. But, as I’ve discussed in previous articles, the language you use and style of your writing creates and impression of you and your firm. When used correctly, punctuation helps clarify our information. Here, we offer some practical, easy-to-remember guidelines that can help.

The Comma

Use a comma to separate thoughts within a sentence, particulary in longer sentences.

For example, the following statement is confusing because the sentence has no internal punctuation:

When we investigated the site on August 12, 2005 at the request of Mr Connaught and the Executive Committee we immediately concluded that the low level of the land would cause flooding during heavy rainstorms.

But if we insert two commas to separate the thought about who requested the investigation, the sentence becomes much clearer:

When we investigated the site on August 12, 2005, at the request of Mr Connaught and the Executive Committee, we immediately concluded that the low level of the land would cause flooding during heavy rainstorms.

We are often asked whether you should insert a comma before the last item in a list of three or more items within a sentence, like this:

The committee approved the purchase of five desktop computers, three LCD monitors, and two laser printers.

The Semicolon

Treat semicolons as if they were periods. This means there must be a complete thought (i.e. the equivalent of a complete sentence) on either side of a semicolon.

The investigation resulted in unexpected results that disproved our theory ; seven of the test samples showed traces of pollution.

A semicolon is acceptable here because there is a direct connection between the two thoughts. Note that you do not capitalize the first letter of the word that follows the semicolon.

Use a colon with a subheading or to introduce a list, a quote, or a statement. What follows is an explanation of what came before it.

Special care must be taken when opening the printer cover: the element will be extremely hot.

As with the semicolon, you do not capitalize the first letter after a colon that is embedded within a sentence.

When you insert a colon at the end of a sentence to introduce a list, the words that precede the colon must form a complete sentence:

When the project is complete, we will provide you with the following documents:
1. Three copies of a report outlining the building's condition.
2. A proposal for renovating the building.
3. An estimate of the cost to implement the proposed renovations.

Note that each entry after the colon starts with a capital letter and ends with a period. However, a different rule applies if the introductory statement does not form a complete sentence:

• A colon is not inserted at the end of the introductory sentence (it is left open).
• Each statement following the introductory sentence does not start with a capital letter; it also ends with a comma instead of a period (except for the last statement).
• The word “and” is inserted after the comma at the end of the second-last sentence.

Here's an example:

When the project is complete, we will provide you with
1. three copies of a report outlining the building's condition,
2. a proposal for renovating the building, and
3. an estimate of the cost to implement the proposed renovations.

The colon is omitted, and the periods are replaced with commas, because an open list like this is really exactly the same as a full sentence:

When the project is complete we will provide you with three copies of a report outlining the building's condition, a proposal for renovating the building, and an estimate of the cost to implement the proposed renovations.

There is no “right way” to present information like this: much will depend on how easily you want your readers to access it. You have several choices.

Online instruction in technical writing is available at www.rgilearning.com

© 2005, RGI Learning

Lisa Moretto is the President of RGI Learning, Inc. For 14 years she has helped engineers improve their oral and written communication skills. Visit www.rgilearning.com or call (585) 461-3617 to learn about RGI’s courses.

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