when something will definitely happen► certainly/definitely use this to say that you are completely sure that something will happen or that someone will do something. Definitely is more common in spoken English than certainly: · I'll certainly be glad when this course is over.· Roger and Andy are definitely coming, but I'm not sure about Nancy.· We'll certainly be back by 7 o'clock.· Owen is injured and will definitely miss the game on Saturday.
► for sure informal if you say that something will happen for sure , you mean it will certainly happen: · Yeah, you'll see him. He'll be there for sure.· Milan are going to win the cup for sure. They're just such a strong team.that's for sure: · She'll come home when she runs out of money, that's for sure.
► be bound to/be sure to/be certain to if something is bound to happen it is certain to happen, especially because that is what always happens: · The kids are bound to be hungry when they get home -- they always are.· My car broke down today. It was bound to happen sooner or later.· Have you asked Ted? He's sure to know.· The drop in prices and lack of demand are certain to affect the manufacturing industry.
► it's only/just a matter of time use this to say that something is certain to happen but no one knows exactly when: · You'll learn how to do it eventually -- it's only a matter of time.· Your father is dying and there's nothing we can do. I'm afraid it's just a matter of time.it's only/just a matter of time before: · It was only a matter of time before Lynn found out Phil's secret.
► cut and dried if something is cut and dried , it is certain to happen in a particular way because it has already been planned or decided, and nothing can be done to change it: · My future was cut and dried. I would join my father's firm, and take it over when he retired.· We made the arrangements weeks ago. It's all cut and dried.
► be a certainty if something is a certainty , it is certain to happen, especially because the situation has changed and made it certain: · Johnson was the fastest man on earth, and a gold medal seemed a certainty.· Being left alone in her old age, the fate she had always feared, now became a certainty.
► be a foregone conclusion if something, especially a result, is a foregone conclusion, it is certain to happen even though it has not yet been officially decided: · Ian's bound to get the job -- it's a foregone conclusion.· The outcome of the battle was a foregone conclusion.
a situation, decision, result etc that is cut and dried cannot now be changed: 
I don’t think the plan is as cut and dried as people think.