say it: AHP-tuh-muhm
optimum is a noun and adjective meaning "most favorable conditions or greatest degree or amount possible under given circumstances". It carries 2 recorded senses.
most favorable conditions or greatest degree or amount possible under given circumstances
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for optimum come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.