be only a matter of time
US /bi ˈoʊnli ə ˈmætər əv taɪm/
UK /bi ˈoʊnli ə ˈmætər əv taɪm/
1.
used to say that something is certain to happen, but you do not know exactly when
:
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It will be only a matter of time before they find out the truth.
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With his talent, it's only a matter of time until he becomes famous.