Subscribe to The Chicago Manual of Style Online
Q. In the phrase “today, tomorrow, & always” should the comma before the ampersand be removed?
A. Though the serial comma has officially been Chicago style since 1906 (when the first edition of the Manual was published), we prefer to omit it before an ampersand (see CMOS 6.21). The serial comma—the one before the conjunction in a series of three or more (it’s also known as the Oxford comma)—suggests thoroughness (some consider it to be unnecessary); the ampersand, by contrast, is an abbreviation (derived from the Latin word et, or “and”). The two together, then, make for an odd pairing of the thorough and the minimal. Either remove the comma or spell out the word “and.”