unless or until

The boy will not do well in the exam ,unless or until, he studies hard.
Is this sentence correct?

Hi Xamba,

There is a difference between the two. 'Unless; suggests if he doesn’t study hard, he will not do well. ‘Until’ suggests that as soon as he studies hard, he will do well. In other words ‘unless’ is conditional and ‘until’ is temporal. At the same time both are grammatically correct.


Thank you very much sir for anwsering my question.