Unless = if not, except when.
Unless = if not, except when. ‘ Unless ‘ is not used in imaginary/unreal or hypothetical situations. ‘ Unless ‘ negates a sentence and therefore no further negation is required by adding No/None/Not etc as in the case of ‘ If’.
- Unless you work hard, you will not pass the exam.
- I will not go to the party unless I am invited.
- If he weren’t so stupid , he would understand it. ( here we don’t use ‘ Unless’ as it is an imaginary or hypothetical situation)
- Unless it rains, he goes for a walk everyday.
- I will lend you my camera unless my brother wants it for his use.
- If she hadn’t misbehaved, I would have helped her. ( you cannot use ‘Unless’ here)
- Students are not allowed to conduct the risky experiment themselves unless they are under the supervision of a teacher.