Learn Hardcore Italian: È importante che tu sappiA quando tirare la maniglia di emergenza. - It’s important that you know when to pull the emergency handle.

Because after È importante che Italian requires the subjunctive to express necessity, importance or advice in a dependent clause. Using sai (indicative) would be grammatically incorrect here.

What is the function of che in this sentence?

Che is a conjunction meaning that. It introduces the subordinate clause and triggers the subjunctive mood: “It’s important that you know…”

Why is the subject pronoun tu used before sappia? Is it mandatory?

Italian often omits subject pronouns, since the verb ending already indicates the subject. Including tu adds emphasis or clarity (e.g. distinguishing “you” from someone else). It’s not mandatory; you could also say È importante che sappia…, but then it sounds more impersonal or formal.

How does sapere combine with quando and the infinitive tirare?

Here sapere (to know) is in the subjunctive (sappia) because of che, followed by quando + infinitive (tirare). This structure means “to know when to do something.” In English: “It’s important that you know when to pull…”

Does tirare always mean “to pull,” or can it have other meanings?

Primarily tirare means to pull, but context can give it senses like to draw, to drag, to fire (a gun), or to operate. In tirare la maniglia di emergenza, it specifically means “pull.”

Could we rephrase the sentence without using the subjunctive mood?

Yes. You can use an impersonal construction: È importante sapere quando tirare la maniglia di emergenza. Here sapere stays in the infinitive and you avoid the subjunctive and the explicit tu.

What’s the difference between sapere and conoscere in this context?

Use sapere for knowing facts, information or how to do something (“know when to pull”). Conoscere is for being familiar with people, places or things, so it wouldn’t work here.