quando

Quando has three jobs and they are easy to keep apart once you have seen them. It is the interrogative "when?" in direct questions and in indirect ones after verbs of asking and not knowing. It is a causal conjunction "since, seeing that", usually strengthened to quandoquidem, and in that sense it takes the indicative. And after si, nisi, ne and num it loses its question force entirely and means "ever": si quando is "if at any time".

What it is NOT is the ordinary narrative "when". For that Latin reaches for cum, with the subjunctive in past narrative, or for ubi and postquam with the indicative when the point is simple sequence. A learner who uses quando for every English "when" will be understood and will sound wrong.

It is the ancestor of Italian and Spanish cuando, quando and French quand, which took over the narrative job the classical language had reserved for cum.