ninetieth

adjective

1. next after the eighty-ninth; being the ordinal number for 90.
2. being one of 90 equal parts.

noun

3. a ninetieth part, especially of one (1/90).
4. the ninetieth member of a series.

adjective

1. (usually prenominal)
   1. being the ordinal number of ninety in numbering or counting order, position, time, etc. Often written: 90th
   2. (as noun)the ninetieth in succession

noun

2. 1. one of 90 approximately equal parts of something
   2. (as modifier)a ninetieth part
3. the fraction equal to one divided by 90 (1/90)

late 14c., nyntithe; see ninety + -th (1). Replaced Old English nigenteoþan.