quantile

Quantiles are cutpoints dividing a set of observations into equal sized groups. There are one fewer quantiles than the number of groups created. Thus quartiles are the 3 cut points that will divide a dataset into four equal-size groups. Common quantiles have special names: for instance quartile, decile (creating 10 groups: see below for more). The groups created are termed halves, thirds, quarters, etc., though sometimes the terms for the quantile are used for the groups created, rather than for the cut points.