Sometimes we save space, or typing, by using a number with a suffix:
57th Street
That’s perfectly legitimate, and for larger numbers it’s probably easier to read than spelling the whole thing out:
Fifty-Seventh Street
But we do have to be careful to remember that both the numbers and the letters represent sounds. The number “20” is pronounced “twenty,” for example. So what do we make of this?
A porch near the New Hamburg train station in New York is occupied by strange mannequins dressed in 20ies fashion.
There are many people who absorb information from written text without ever hearing the sounds of the words, and perhaps they won’t see anything wrong with that. But if you were to read that sentence out loud, actually reading all the characters the writer has put in it, this is what you would say:
A porch near the New Hamburg train station in New York is occupied by strange mannequins dressed in twenty-eez fashion.
When you make a number plural, just add an S to it. That’s enough, and anything more is too much.
We have to be similarly careful about making ordinal numbers—like “57th,” for example. That’s fine, but what would you say to these?
The 51th Annual Golden Apple Awards
51th Meeting of the UNWTO Commision for Europe
51th Anniversary Meeting of the Clay Minerals Society
The Editor found “About 473,000 results” for “51th” on Google. But we don’t say “fifthy-oneth.” We say “fifty-first.” That little “th” is wrong, and rather funny to someone who actually hears the sounds of words.
Similarly,
52th meeting of IPDC Bureau
52th WWC Board of Governors Meeting
52th Commonwealth Parliamentary Conference
…and about 233,000 other results for “52th.” We say “fifty-second,” not “fifty-twoth.” Shall we try our luck with 53?
53th District of California
53th anniversary of the Berlin Wall
Kirklin takes charge of Corps, named 53th QM General
We say “fifty-third,” not “fifty-threeth.”
For numbers that end in 1, 2, or 3, adding “th” to the end won’t work. Here’s how to add the right suffixes:
51st
52nd or (less common) 52d
53rd or (less common) 53d.
But wait! Don’t those suffixes violate the fundamental rule above—namely that both the number and the letters are pronounced?
Yes, they do. Life isn’t always fair. We don’t say “fifty-twond.” We’re stuck with the fact that the ordinal numbers first, second, and third are completely different words from the cardinal numbers one, two, and three. But these suffixes are the traditional way of abbreviating those ordinal numbers, so we don’t provoke snickers from the audience.