certain event

Short definition from Wiktionary

Noun

1. 1
   An event that contains all of the possible outcomes and thus is known a priori to be certain to occur;
2. 2
   An event that contains all of the possible outcomes and thus is known a priori to be certain to occur; (more formally) the entire sample space (which by definition has measure 1 and probability 1); said sample space with the exclusion of, at most, a set of measure 0 (thus retaining measure 1): the entire sample space (which by definition has measure 1 and probability 1); said sample space with the