Percentile
Etymology
A blend of “percent” (Latin “per centum,” by the hundred) with the “-ile” of “quartile.” The concept was introduced by Francis Galton in 1885 as part of his work on ranking human variation.
noun · /per-SEN-tyl/
A value below which a given percentage of the data falls, as in “the 90th percentile.”
What it names
It locates you within a crowd rather than on an absolute scale, which is how ranks, test scores, and growth charts actually work.
Example
A baby in the 90th percentile for weight is heavier than 90 percent of babies its age — a rank, not a grade to pass or fail.
Related idea
A percentile is a kind of quantile and describes position, not amount; being in the 99th percentile of wealth says nothing about the dollar gap to the person in the 98th, which can be vast.