Learn Spanish (Latin America): Aunque estés cansado, tienes que atar el silbato a la mochila. - Even if you are tired, you have to tie the whistle to the backpack.

When aunque is followed by the subjunctive, it describes a hypothetical or unverified situation, translating to 'even if'. So aunque estés cansado means 'even if you might be tired'. If we used the indicative here (aunque estás cansado), it would declare a known fact, meaning 'although you are tired'.

Could I say Aunque seas cansado instead?

No, you need to use the verb estar because being tired is a temporary physical state or condition. Therefore, we use estés, the subjunctive form of estar, rather than seas (which comes from ser).

Why is there a que in tienes que atar?

In Spanish, to say you 'have to' or 'must' do something, you use the fixed phrase tener que followed by an infinitive (unconjugated) verb. Here, tienes que gives us 'you have to', and atar is the infinitive 'to tie'.

Why do we use the preposition a in atar el silbato a la mochila?