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