eighteenth

adjective

1. next after the seventeenth; being the ordinal number for 18.
2. being one of 18 equal parts.

noun

3. an eighteenth part, especially of one (1/18).
4. the eighteenth member of a series.

adjective

1. (usually prenominal)
   1. coming after the seventeenth in numbering or counting order, position, time, etc; being the ordinal number of eighteen: often written 18th
   2. (as noun)come on the eighteenth

noun

2. 1. one of 18 approximately equal parts of something
   2. (as modifier)an eighteenth part
3. the fraction that is equal to one divided by 18 (1/18)

adj.

mid-13c., egtetenþe, modified, by influence of eighteen, from Old English eahtateoða; from eight + teoða “tenth” (see -ty (1)).