certain in WordNet English dictionary

1. 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"
   certain 
   
2. 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"
   certain  sure 
   
3. certain to occur; destined or inevitable
   "he was certain to fail"; "his fate is certain"; "In this life nothing is certain but death and taxes"- Benjamin Franklin; "he faced certain death"; "sudden but sure regret"; "he is sure to win"
   certain  sure 
   
4. established irrevocably
   "his fate is sealed"
   sealed  certain 
   
5. exercising or taking care great enough to bring assurance
   "be certain to disconnect the iron when you are through"; "be sure to lock the doors"
   certain  sure 
   
6. 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"
   certain 
   
7. reliable in operation or effect
   "a quick and certain remedy"; "a sure way to distinguish the two"; "wood dust is a sure sign of termites"
   certain  sure