Unless-If | Commonly Confused Words

Unless

/ʌnˈles/

Used to say that something will happen or be true only if another thing happens or is true.

'Unless we kill her,' said Raymond.She was all alone, unless he came to her now.Of course, unless you have some special reasons to..."

This word has no antonyms

A word used to introduce a condition or a possibility

I can't tell if he's messing around or legitimately annoyed.Ned worked quickly to set if free.Or, if he did it meant the loss of Hortense.

This word has no antonyms

Unless is often used in negative contexts, while if is used in both positive and negative contexts.
You often use unless to specify an exception, whereas if sets a condition for something to happen or not happen.
Think of unless as excluding, while if is including or introducing a condition.
In many cases, you could replace unless with if...not, but not vice versa.
Unless can often mean except if, adding a restrictive condition.