eighteen, n. & adj.
1 one more than seventeen, or eight more than ten; the product of two units and nine units.
2 a symbol for this (18, xviii, XVIII).
3 a size etc. denoted by eighteen.
4 a set or team of eighteen individuals.
5 (18) Brit. (of films) classified as suitable for persons of 18 years and over.
--adj. that amount to eighteen.
eighteenth adj. & n.
OE ehtatene, eaht-