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make sure (of something)
to check something and be certain about it. Please make sure of your facts before you write the report. We made sure of the route we had to follow before we left. Please double-check and make sure.
1. Make certain, establish something without doubt, as in Make sure all the doors are locked. It is also put as make sure of, as in Before you make that speech, make sure of your facts. This usage was first recorded in 1565.
2. make sure of. Act so as to be certain of something, as in He wanted to make sure of his own district before seeking support elsewhere. This usage was first recorded in 1673.
make ˈsure (of something/that...)
1 check that something is true or has been done: I think the door’s locked, but I’d better go and make sure. ♢ Have you made sure that we’ve got enough money?
2 do something in order to be certain that something else happens: I want to make sure that the party is a success. ♢ Make sure there’s enough to eat tonight.
To establish something without doubt; make certain: Make sure he writes it down.