Conditionals with "Unless"

The word unless basically means the same thing as if ... not. For example, "Unless you study, you will fail" means the same thing as "If you do not study, you will fail."

Unless is often used in conditional sentences. It can be used with the first, second, or third conditional. Here are some examples.

First Conditional: "You'll be unhappy unless you break up with her" = "You'll be unhappy if you do not break up with her."

Second Conditional: "I wouldn't ask her out unless you told me it was OK" = "I wouldn't ask her out if you told me it was not OK."

Third Conditional: "They wouldn't have come over unless we'd invited them" = "They wouldn't have come over if we had not invited them."