[ことがある, kotogaaru] (exp, v5r-i) (1) (uk) (after the past tense form of a verb) (something) has occurred; to have done (something); such a thing happened; (2) (uk) (something) happens on occasions; there are times when; (P)
[ことがない, kotoganai] (exp, adj-i) (1) (uk) (after the past tense form of a verb) (something) has never occurred; to have never done (something); such a thing has not happened; (2) (uk) never happens; there is never a time when
[ことにする, kotonisuru] (exp, vs-i) (1) (uk) to decide to; (2) (uk) (after the past tense form of a verb) to pretend that; (3) (uk) (as 〜ことにしている) to make a practice of doing; to make it a rule to