Commas Used in Elliptical Constructions.
Commas indicate a slight pause. In an elliptical construction—a sentence in which a word has been left out—commas usually fill in the gap. Usually! There is the dreaded exception—sometimes the meaning is clear without the comma, no pause occurs naturally in reading the sentence, and therefore, no comma is needed.
Examples are always helpful. Here’s a sentence with elliptical construction:
I moved here from Colorado; Jeff, from Florida; and Sally, from Alaska.
The sentence actually has three clauses:
- I moved here from Colorado
- Jeff moved here from Florida
- Sally moved here from Alaska
In the last two, however, words are missing. The comma has been inserted to show where those understood words belong.
Here’s another example:
In professional basketball teams play eight-two games; in football, sixteen; in baseball, one hundred sixty-two.
Sometimes the meaning of a sentence is so clear, the commas aren’t needed.
One writer is good at characterization, another at plots, and a third at setting.
I’m inclined to think that the presence of a pause should be your guide. You might feel like you’re “just guessing,” but your decision will be based on the purpose of the comma—it’s there to tell the reader to take a breath or at least to take a break, a slight one.