Percentiles

Part of speech: noun

Definitions

1. A statistical measure indicating the value below which a given percentage of observations in a group falls
2. A point in a distribution divided into 100 equal parts, each representing one percentage
3. A term used in analysis to identify relative standing in a data set, denoting how many scores are below a specific score

Etymology: Francis Galton, the Victorian polymath better known for his work on heredity and fingerprints, coined "percentile" in 1885. He built it from "percent" and the suffix "-ile", so the word is a deliberate statistical invention rather than something that grew up in ordinary speech. The suffix is the interesting part. "-ile" comes from Latin "-ilis", meaning "relating to" or "capable of", and it appears in words like "juvenile" and "versatile." Galton used it to mark a position on a scale of one hundred, so that a score at the 90th percentile sits above nine-tenths of the data. The word's meaning is therefore plain arithmetic: it names a rank, not a quantity.

Synonyms: percentages, proportions