eighteen

American  

[ey-teen] / ˈeɪˈtin /

noun

1. a cardinal number, ten plus eight.

2. a symbol for this number, as 18 or XVIII.

3. a set of this many persons or things.

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adjective

1. amounting to 18 in number.

eighteen British  

/ ˈeɪˈtiːn /

noun

1. the cardinal number that is the sum of ten and eight and the product of two and nine See also number

2. a numeral, 18, XVIII, etc, representing this number

3. the amount or quantity that is eight more than ten

4. something represented by, representing, or consisting of 18 units

5. (functioning as singular or plural) a team of 18 players in Australian Rules football

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determiner

1. 1. amounting to eighteen

      eighteen weeks

   2. ( as pronoun )

      eighteen of them knew

Etymology

Origin of eighteen

before 1000; Middle English ehtetene, Old English eahtatēne; cognate with Old Norse āttjān, German achtzehn. See eight, -teen

Example Sentences

“I am eighteen years old, and I live with my sister Constance. . . . Everyone else in my family is dead.”

From The Wall Street Journal • Nov. 14, 2025

He travelled eighteen miles but only after ejecting every loose object from the balloon to enable it to launch.

From Salon • Nov. 3, 2024

In mice, this can be a period of up to eighteen months, while in humans it can last almost half a century, the average time between birth and menopause.

From Science Daily • Feb. 20, 2024

“For the crime of murder in the first degree, the Legislature has deemed the mandatory imposition of life without the possibility of parole to be the appropriate punishment for adults eighteen and older.”

From Seattle Times • Jan. 11, 2024

But events unfolded quickly when, eighteen days later, Richmond fell, and then General Lee surrendered.

From "Chasing Lincoln's Killer" by James L. Swanson