Q. When is it proper to use an ampersand? Thank you.
A. In edited prose, use of the ampersand—&*—is normally limited to
- terms like R&D and Q&A that are always spelled with an ampersand (see also CMOS 10.10);
- corporate names like AT&T and Simon & Schuster that reflect the usage of a particular company or brand (see also CMOS 10.24); and
- ampersands in verbatim quotations.
An ampersand may also be used when mentioning the title of a work that includes one (subject to editorial discretion; see CMOS 8.165). And if you’re working with HTML, you may need an ampersand in a character reference like (for a nonbreaking space)—or & (for an ampersand).
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* According to the OED (and other sources), the ampersand evolved from a stylized rendering of the Latin conjunction et (and) in the form of a ligature, and the word ampersand is an English-language corruption of “& (and) per se and” (“and by itself [is] and”)—a phrase that differentiated the symbol from &c., an old-fashioned way of writing et cetera (and others).