certainI feel certain that this change will be for the best.
know/say for certainI can't say for certain, but I think he's coming to the party.
sureDon't worry - I'm sure it won't be a problem.
positive"Are you sure you let the cat in?" "I'm positive."
be sure ofHe's the one who stole my bike - I'm sure of it!
for sureOne thing's for sure: I'll never go on a date with her again.
beyond a shadow of a doubtIt has been proved beyond a shadow of a doubt that the medication is effective.
it's safe to say (that)I think it's safe to say that he will win a majority of votes.
no doubtYou will no doubt want to see the evidence.
boundHe's bound to have the spare parts around.
I'll be boundUKold-fashionedHe's on holiday, I'll be bound.
confidentI am confident that doctors will find a cure.
convincedPolice are convinced they have the right suspect in custody.