What does eighteen mean?
Eighteen is the cardinal number equal to eight plus ten, written numerically as 18. It functions both as a determiner-like numeral modifying nouns (an eighteen-hour flight) and as a noun in its own right (a group of eighteen; two eighteens on the scorecard). Culturally, eighteen holds special weight across the English-speaking world because it commonly marks the age of legal majority — the point at which a person may vote, sign contracts, marry without parental consent, and otherwise act as an adult. The word follows the transparent pattern of English 'teen' numbers, combining 'eight' and 'ten' exactly as its form suggests, though the vowel shortens slightly in speech. Because it is so easily confused in fast speech with 'eighty', careful pronunciation places primary stress on the second syllable. Eighteen is a neutral, everyday word used freely in all registers.
Equivalent to the product of two and nine, or the sum of eight and ten; one more than seventeen.
"The marathon route covered eighteen miles through the countryside."
The number 18, especially as a figure, an age, or a set of eighteen people or things.
"Eighteen is the minimum age to enlist in many armed forces."
Pluralizes normally when referring to sets or ages: 'the team's two eighteens', 'men in their late eighteens' (less common than 'in his teens').
Used only when referring to multiple instances of the number, figures, or people aged eighteen — never when eighteen modifies a noun.
"The dice showed a pair of eighteens across the three rolls."
In most English-speaking countries, turning eighteen is the legal threshold into adulthood — one syllable-stressed word that unlocks voting, contracts, and independence.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of eighteen
Eighteen descends from Old English 'eahtatīene', a straightforward compound of 'eahta' (eight) and 'tīene' (ten), formed by the same pattern that produced all the other -teen numerals. Its closest cognates are the corresponding Germanic compounds such as German 'achtzehn' and Dutch 'achttien', which reflect the same Proto-Germanic roots for eight and ten. The word has remained remarkably stable in form and meaning throughout the history of English.
How eighteen is actually used
As a numeral it functions attributively before nouns (an eighteen-mile hike) without plural inflection. As a noun it takes normal plural behavior (in their eighteens). The '-teen' ending carries secondary stress, which distinguishes it clearly from 'eighty'.
Easily confused with eighteen
Eighteen is the number 18, while eighty is the much larger number 80; they differ in stress placement — EIGHteen versus eighTY.