Q: I’m confused when addressing letters. When do you use numerals and when do you spell the number out? If you use numerals, do you need the “st,” “nd,” “rd,” and “th” endings? Can “d” alone suffice for “nd” and “rd”? Do you need superscript or is regular type OK? Help!
A: If you want to be formal, The Chicago Manual of Style (15th ed.) recommends that the name of a numbered street or thoroughfare should be spelled out if it’s one hundred or less (as in “First Avenue” or “Ninety-fifth Street”) and given in figures if it’s over one hundred (“122nd Street”).
However, if you’re not writing for publication and you’re simply addressing a letter, you can be more relaxed in using figures instead of spelled-out numbers.
You might, for example, follow New York Times style. The Times spells out numbered street names from “First” through “Ninth” and uses figures for “10th” and above.
The Times also uses “st,” “nd,” “th,” and “rd” with figures where appropriate: “21st Street,” “12th Avenue,” “52nd Road,” “73rd Street,” etc.
In ordinary news copy the newspaper spells out “Street,” “Avenue,” “Road,” and so forth. But in addressing a letter, according to the Chicago Manual, abbreviations are fine: “St.” and “Ave.” and “Rd.”
When we went to work at the Times in the early ’80s, the paper used “d” alone for the endings of ordinal numbers in addresses like “73d Street” and “52d Road”), but the latest Times stylebook recommends “nd” and “rd” endings.
This is a matter of style, not grammar, so the choice is yours. In legal writing, for example, “2d” and “3d” are the standard abbreviations used in citing court cases, but that doesn’t mean lawyers necessarily address their letters that way!
A Google search indicates that “2nd” is much more popular than “2d,” but another search finds that “3d” is far more popular than “3rd” (this is misleading, though, since many “3d” references are abbreviations of “three dimensional”).
As for superscript, it’s not necessary in street addresses, but again the choice is up to you.