Breakdown of Jugaré al billar, a menos que estés ocupado.
estar
to be (location/state)
ocupado
busy
al
to the
jugar
to play
Questions & Answers about Jugaré al billar, a menos que estés ocupado.
Why does a menos que trigger the subjunctive estés in this sentence?
The phrase a menos que (unless) introduces a condition of exception, meaning the main action (jugaré) will happen as long as the condition (estés ocupado) doesn't get in the way. Because it represents a hypothetical obstacle rather than an established fact, a menos que always forces the verb into the subjunctive mood.
Is it possible to use the indicative estás if I am absolutely certain you are busy?
No. While some triggers (like aunque) let you choose between the indicative and subjunctive depending on how certain you are, a menos que is a strict rule. It always takes the subjunctive, no matter the context, so you must always use estés here.
Could I swap a menos que with salvo que or a no ser que here?
Absolutely. Salvo que estés ocupado and a no ser que estés ocupado mean exactly the same thing. They are fully interchangeable with a menos que and also strictly require the subjunctive.
Why is it jugaré al billar instead of just jugaré billar?