forty

American  

[fawr-tee] / ˈfɔr ti /

noun

forties plural

1. a cardinal number, ten times four.

2. a symbol for this number, as 40 or XL or XXXX.

3. a set of this many persons or things.

4. forties, the numbers, years, degrees, or the like, from 40 through 49, as in referring to numbered streets, indicating the years of a lifetime or of a century, or degrees of temperature.

   His office is in the West Forties. Her parents are in their forties. The temperature will be in the forties.

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adjective

1. amounting to 40 in number.

forty British  

/ ˈfɔːtɪ /

noun

1. the cardinal number that is the product of ten and four See also number

2. a numeral, 40, XL, etc, representing this number

3. something representing, represented by, or consisting of 40 units

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determiner

1. 1. amounting to forty

      forty thieves

   2. ( as pronoun )

      there were forty in the herd

Etymology

Origin of forty

before 950; Middle English fourti, Old English fēowertig (cognate with Old Frisian fiuwertich, Old High German fiorzug, German vierzig ). See four, -ty ¹

Explanation

Whether you call it 40 or XL, you're talking about forty: the number between thirty-nine and forty-one. If you’ve ever seen the Roman numeral XL, that means forty, since X equals ten, L equals 50 and if you put the X before the L it means L minus X or 50 minus 10 — which is 40. This number comes up in the Bible a lot, especially when the earth is said to have been flooded for forty days and forty nights. Most people are not that thrilled to turn 40 years old: it means they're middle-aged.

Example Sentences

That changed when an international team returned to the site using modern technology unavailable to scientists forty years earlier.

From Science Daily • May 20, 2026

In our town, we’re told in the new LA28 announcement of the Cultural Olympiad: “It’s been forty years. Los Angeles is ready to do it again.”

From Los Angeles Times • May 11, 2026

There was no reason I couldn’t close the laptop for forty minutes.

From Salon • Feb. 19, 2026

The middle-aged artist appears in the picture’s foreground while behind her “are three small figures, dressed in the winter clothing of the girls of forty years ago.”

From The Wall Street Journal • Feb. 3, 2026

Now I was due at the store in forty minutes, and there was nothing to do but break it to her outright.

From "The Red Car to Hollywood" by Jennie Liu