Pants, measles, and scissors.
Today’s topic is when plurals have no singular.
A listener named Brent called in with this question: "I have a question: how come pants, trousers, slacks, corduroys are all plurals even though there is only one of them?"
Nouns are sociable. They like to be more than singular. A tooth hangs out with teeth, a matrix is bored without the company of matrices, and a crisis can’t wait to mingle with other crises. Even proper nouns that are the names of places and people enjoy being a few instead of one:
“There are too many Henriks in this boat for my taste,” said Daphne.
But in every community there is the exception, and a plural noun may refuse to be singular (1) like those in Brent's examples. This type of nouns is known as a defective noun, also called a plurale tantum. The appearance of these words is more the effect of time on language than the fault of lexicographers. Besides occurring in English, defective nouns also occur in Arabic, Greek, and Latin.
Is There a Singular Form for Measles?
Let's start with the measles, the name for the nasty childhood illness that's caused unknown days of missed schooling, comes from the Middle English mesele (2).That was the name given to the red circle characteristic of the highly contagious disease. But since the mesele rarely showed up as one, its plural came into use and shoved out the singular. Measles is a noun that can take a singular or a plural verb. You could say, “Measles is caused by a virus,” or “The measles are making Daphne crazy.”
Scissors Or Scissor?
On to scissors! The Latin had it right when this cutting tool was called the "ciscoria," with a "c," which meant "cutting instrument." Sometime in the 16th century, the word started being spelled with an "s" instead of a "c" ("sisours"), because it became confused or intermingled with the Latin word "scissor" (with an "s" like we spell it today), which means "tailor." You can call the two-bladed cutting tool simply scissors or you can call it a pair of scissors.