index number is a noun meaning "a number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of time". It carries one recorded sense.
a number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of time
Definitions, synonyms and semantic relations for index number come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.