Definify.com
Webster 1913 Edition
Eighteenth
1.
Next in order after the seventeenth.
2.
Consisting of one of eighteen equal parts or divisions of a thing.
Eight′eenthˊ
,Noun.
1.
The quotient of a unit divided by eighteen; one of eighteen equal parts or divisions.
2.
The eighth after the tenth.
Webster 1828 Edition
Eighteenth
EIGHTEENTH
,Adj.