Decile

noun

1. Any of the values in a series that divides the distribution of individuals in that series into ten groups of equal frequency.

   "Although few people scored high marks, everyone did quite well—the lowest decile was over 50%."

2. Any one of the ten subsets or groups so divided.

   "Our school is in the top decile for exam results."

3. An aspect or position of two planets when they are distant from each other a tenth part of the zodiac.