Q: In a book of mine about triathlon training for women, I used the short “tri” many times and I pluralized it as “tris.” But my daughter tells me that I should have used an apostrophe, making the plural “tri’s.” Is she right?
A: No, it’s incorrect to form the plural of a noun by adding an apostrophe plus “s.” So writing “tri’s” for the plural of “tri” would be like writing “apple’s” for the plural of “apple.”
You’d write the possessive as “tri’s” (as in “the “tri’s fourth year”), but the plural would be “tris.”
Ordinarily, “tri” is a prefix, not a word in itself. When you decide to use a prefix as a short form for an entire noun, you pluralize it the same as you would any other noun – usually by adding “s” or “es.”
So “sub” (short for “submarine”) would be pluralized as “subs,” “ex” (for “ex-husband”) as “exes,” “semi” (“semi-trailer truck”) as “semis,” and so on.
The Oxford English Dictionary doesn’t have an entry for “tri” as short for “triathlon,” but it does have one for “tri” as a clipped word for “trimaran,” a boat with a central hull and a float on each side.
The OED describes a triathlon as “an athletic or sporting contest composed of three different events.”
In the dictionary’s earliest citation, dating from 1973, the three events are “clay pigeon shooting, fly fishing and riding a handy hunter-course over jumps.” The events are now usually swimming, cycling, and running.
With some prefixes (like “tri” for “triathlon” or “trimaran”), the plural may not be familiar to readers. But follow the rules you must! (This means you have to tri harder.)
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