Parentheses vs. Commas

I got a follow-up question about the i.e. and e.g. reprise I sent out Tuesday. Lori asks:
“In your examples, e.g. was in parentheses and i.e. was not. Is there a rule about when to use parentheses and when to use commas with these abbreviations?”

Well, Lori, the use of parentheses doesn’t depend on whether it was i.e. or e.g., but how either one is used in the sentence. A parenthetical expression adds supplemental information to the sentence, such as background, asides, tangents, afterthoughts and other related matter that could be left out entirely and have the sentence still make perfect sense.

Examples:
The company hires many geoscientists (i.e., geologists and geophysicists).
The company hires many engineers, e.g., mechanical, chemical, and petroleum engineers.

Basically, either one could go either way, using either commas or parentheses depending on the emphasis you want to give the material.

The AP Stylebook says to use parentheses sparingly.
“Parentheses are jarring to the reader. … If a sentence must contain incidental material, then commas or two dashes are frequently more effective. Use these alternatives whenever possible.”

However, em dashes tend to emphasize the text in between them, whereas parentheses tend to de-emphasize the text in between them, and commas tend to imply the same emphasis as the rest of the sentence.

Examples:
The 50-km pipeline runs from Point A—in the jungle—to City B on the coast.
The 50-km pipeline runs from Point A (in the jungle) to City B on the coast.
The 50-km pipeline runs from Point A, in the jungle, to City B on the coast.

Punctuation Rules for Parentheses:
If there is a full sentence inside them, put the period or question mark inside.
If there is an incomplete sentence inside them, put the period or question mark outside.

Examples:
Next, we developed a crossplot of porosity and permeability. (This is Step 5 in the workflow.)
Next, we developed a crossplot of porosity and permeability (Figure 5).

Two more rules about parentheses:
Parenthesis is singular, but they usually come in pairs, which are called parentheses.
Make sure you have two of them and that they are facing each other!

————————————–
Astute Quote of the Day:
“I hold that the parentheses are by far the most important parts of a non-business letter.”
– David Herbert Lawrence, English writer, 1885-1930
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