Eighteen has 4 different meanings across 4 categories:
Noun · Adjective · Num · Proper Noun
The cardinal number occurring after seventeen and before nineteen, represented in Roman numerals as XVIII and in Arabic numerals as 18.
"The eighteen students gathered in the gymnasium for their annual sports day."
A surname.
"Mr. Eighteen is the head of our local bowling team."
Eighteen comes from Old English, originally meaning "eight" combined with the suffix "-teen." It is related to similar words in other Germanic languages like German and Dutch.