Quantile
Etymology
A twentieth-century statistical coinage from Latin "quantus" (how much), formed by analogy with "percentile" and its "-ile" ending. It is the umbrella term of which those familiar divisions are special cases.
noun · /KWAHN-tyle/
A cut point that divides a ranked set of data into equal-sized groups.
What it names
It gives a general name for any such division — quartiles, deciles, percentiles — letting one talk about position within a distribution independent of the number of slices.
Example
Her test score fell in the top quantile, above ninety percent of the cohort.
Related idea
A percentile is simply a quantile that splits data into a hundred parts; quantile is the parent concept, covering quartiles (four parts), deciles (ten), and any other equal division of a ranking.