decile (adj.)

1670s in astrology, of planets, "one-tenth part of the zodiac distant from one another;" 1882 in statistics; from French décile or Medieval Latin *decilis, from Latin decem "ten" (from PIE root *dekm- "ten") on the model of quintilis, sextilis.

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Definitions of decile from WordNet

decile (n.)
(statistics) any of nine points that divided a distribution of ranked scores into equal intervals where each interval contains one-tenth of the scores;