The ordinal number corresponding to 18; coming after the seventeenth and before the nineteenth in sequence. Used to denote position or rank.
From Old English eahtatēoþa, compound of eahta 'eight' + -tēoþa ordinal suffix. The '-teenth' ending developed in Middle English for numbers 13-19, creating a distinct linguistic pattern for this numerical range.
The 'eighteenth' belongs to that quirky English number family ending in '-teenth' that exists nowhere else in our counting system - we don't say 'twenty-teenth' or 'thirty-teenth.' This linguistic island reveals how the numbers 13-19 were conceptualized differently in early Germanic languages, as a special group beyond the basic ten.
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