- next after the seventeenth; being the ordinal number for 18.
- being one of 18 equal parts.
- an eighteenth part, especially of one (1/18).
- the eighteenth member of a series.
- (usually prenominal)
- coming after the seventeenth in numbering or counting order, position, time, etc; being the ordinal number of eighteen: often written 18th
- (as noun)
- one of 18 approximately equal parts of something
- (as modifier)
- the fraction that is equal to one divided by 18 (1/18)
