Definition of "Certain" :

adjective: exercising or taking care great enough to bring assurance

"Be certain to disconnect the iron when you are through."

adjective: established beyond doubt or question; definitely known

"What is certain is that every effect must have a cause."

adjective: having or feeling no doubt or uncertainty; confident and assured

"Felt certain of success."

adjective: certain to occur; destined or inevitable

"He was certain to fail."

adjective: definite but not specified or identified

"Set aside a certain sum each week."

adjective: reliable in operation or effect

"A quick and certain remedy."

adjective: established irrevocably