unless

used to introduce a condition that is necessary for something else to happen or be true

a menos que, salvo que

• unless + clause

Collocations unless you do sth · unless it rains

• We won't go unless it's sunny.

  No iremos a menos que haga sol.

used to introduce an exception or negative condition in a statement

salvo que, a no ser que

• unless + clause

Collocations unless you know him well · unless there's an emergency

• You can't park here unless you have a permit.

  No puedes estacionar aquí salvo que tengas un permiso.