Q. My question is about the proper use of semicolons. My editor wants me to use the following construct when I use “that is” or “for example”: “You can tailor much of the desktop environment; for example, the background window.”
A. CMOS does not support such use of the semicolon; semicolons—when not separating items in a syntactically complex series—should separate independent clauses:
Deep-dish pizza has anchored me to the Midwest; that is, I’m unwilling to give it up and too heavy to leave.
When an expression like “that is” is used to introduce a dependent clause, use a dash (or two) or parentheses:
Having only one thing in common—namely, a knowledge of English—we decided to call it off.
Snow is great until you have to do something about it (e.g., rescue injured skiers).
Hair loss was not much of a problem outdoors in 1910—in other words, back when you were expected to wear a hat.