Longman Dictionary of Contemporary English homepage

Date: 1200-1300
Language: Old French
Origin: Vulgar Latin certanus, from Latin certus 'decided, certain', from cernere 'to sift, decide'

certain

1 adjective
     
cer‧tain1 S1 W1
1 [not before noun] confident and sure, without any doubts [= sure]
certain (that)
I'm absolutely certain that I left the keys in the kitchen.
I felt certain that I'd passed the test.
certain who/what/how etc
I'm not certain when it will be ready.
certain about/of
Now, are you certain about that?
They were watching him. He was certain of it.
2 if something is certain, it will definitely happen or is definitely trueCOLLOCATIONS COLLOCATIONS
it is/seems certain (that) be/appear/look/seem certain to do something be certain of (doing) something it is not certain whether/how etc almost/virtually/practically certain fairly certain by no means certain/far from certain (=not definite) certain death
It now seems certain that there will be an election in May.
Many people look certain to lose their jobs.
It is wise to apply early to be certain of obtaining a place.
His re-election was considered virtually certain.
It is by no means certain that the deal will be accepted.
If they stayed in the war zone they would face certain death.
3

make certain

a) to check that something is correct or true [= make sure]
make certain (that)
We need to make certain that it's going to fit first.
b) to do something in order to be sure that something will happen [= make sure]
make certain (that)
Secure the edges firmly to make certain that no moisture can get in.
4

for certain

without doubt [= for sure]
know/say (something) for certain
I know for certain it's in here somewhere.
that's/one thing's for certain
One thing's for certain, he won't be back.
5 [only before noun] used to talk about a particular person, thing, group of things etc without naming them or describing them exactly:
The library's only open at certain times of day.
I promised to be in a certain place by lunchtime.
There are certain things I just can't discuss with my mother.
certain kind/type/sort
the expectation of a certain kind of behaviour
in certain circumstances/cases etc
Extra funding may be available in certain circumstances.
6

a certain

a) used to say that an amount is not great:
You may need to do a certain amount of work in the evenings.
to a certain extent/degree (=partly, but not completely)
I do agree with his ideas to a certain extent.
b) enough of a particular quality to be noticed:
There's a certain prestige about going to a private school.
c) formal used to talk about someone you do not know but whose name you have been told:
a certain Mr Franks

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