1cer·tain 
/ˈsɚtn̩/ adjective
/ˈsɚtn̩/ adjective 1 not used before a noun [more certain; most certain] : not having any doubt about something : convinced or sure
▪ Are you certain [=sure] you want to leave today? ▪ I feel less than certain about it. [=I am not sure about it] ▪ She's certain (that) she can do the job despite her lack of experience. ▪ I'm fairly certain that I'll be on time. 2 — used with it to say that something is known to be true or correct ▪ Although little is known about these ancient people, it is certain that they grew a number of crops. ▪ It's not certain [=definite] that the company will lay off workers. [=the company may lay off workers, but it also may not] ▪ It seems certain that the jury will convict him. 3 — used to say that something will definitely happen or that someone will definitely do something ▪ Before the game was half over our team's defeat was nearly certain. ▪ Contact with the poison means certain death. ▪ Her victory seems certain. — often followed by to + verb ▪ As technology develops, the rates of success with the procedure are certain to improve. ▪ Health-care costs are certain [=sure] to increase in coming years. ▪ She is almost certain to win. ▪ He's all but certain to say no. [=he will almost surely say no] 4 always used before a noun — used to refer to something or someone that is not named specifically ▪ Each employee will receive a certain share of the profits. ▪ Building even a simple bookcase takes a certain amount of skill. [=takes some skill] ▪ Certain people are always late for dinner. ▪ On certain days there is no parking on the street. ▪ The new technology has certain limitations. ▪ Students must fulfill certain requirements to graduate. ▪ She's allergic to certain [=particular] foods. ▪ The contract can be extended under certain circumstances. [=in some special cases] ▪ To a certain extent [=up to a point] he's right. ▪ The movie will appeal to people of a certain age. [=people who are no longer young]
▪ Are you certain [=sure] you want to leave today? ▪ I feel less than certain about it. [=I am not sure about it] ▪ She's certain (that) she can do the job despite her lack of experience. ▪ I'm fairly certain that I'll be on time.
a certain 1 — used to refer to a quality that is noticed but that is difficult to explain or describe ▪ She has a certain elegance about her. ▪ The house has a certain charm. 2 formal — used with the name of a person you do not know ▪ In 1889, a certain Mr. Kelly made a large donation to the church.
for certain
: without a doubt : definitely or certainly
▪ No one knows for certain what the outcome will be. ▪ We'll need more than an hour to get there for certain. [=for sure]
▪ No one knows for certain what the outcome will be. ▪ We'll need more than an hour to get there for certain. [=for sure]
make certain
: to do something or find out something so that you have no doubt about whether something is true, correct, will happen, etc.
▪ Make certain (that) you lock the door when you leave. = Make certain to lock the door when you leave. ▪ We must make certain [=make sure] this doesn't happen again. ▪ She made certain she thanked each of them for coming. — sometimes + of ▪ Make certain of your flight times [=be sure that you definitely know your flight times] before you leave for the airport.
▪ Make certain (that) you lock the door when you leave. = Make certain to lock the door when you leave. ▪ We must make certain [=make sure] this doesn't happen again. ▪ She made certain she thanked each of them for coming. — sometimes + of ▪ Make certain of your flight times [=be sure that you definitely know your flight times] before you leave for the airport.
