Real Dictionary

percentile
A percentile is one of the equal divisions of an amount, expressed on a scale from 0 to 100. The 90th percentile of an amount is all amounts between zero percent and ninety percent.

percentile in American English
any of the values in a series dividing the distribution of the individuals in the series into one hundred groups of equal frequency
of a percentile or division into percentiles
adjective: of or pertaining to a percentile or a division of a distribution by percentiles
noun: one of the values of a variable that divides the distribution of the variable into 100 groups having equal frequencies

percentile in British English
noun: one of 99 actual or notional values of a variable dividing its distribution into 100 groups with equal frequencies; the 90th percentile is the value of a variable such that 90% of the relevant population is below that value