say it: SUR-tuhn
certain is an adjective meaning "definite but not specified or identified". It carries 7 recorded senses.
definite but not specified or identified
“set aside a certain sum each week”
“to a certain degree”
“certain breeds do not make good pets”
“certain members have not paid their dues”
“a certain popular teacher”
“a certain Mrs. Jones”
having or feeling no doubt or uncertainty; confident and assured
“felt certain of success”
“was sure (or certain) she had seen it”
“was very sure in his beliefs”
“sure of her friends”
established beyond doubt or question; definitely known
“what is certain is that every effect must have a cause”
“it is certain that they were on the bus”
“his fate is certain”
“the date for the invasion is certain”
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 certain 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.