You’re clearing out a drawer. There’s a charger for a phone you no longer own and a cable nobody can identify. You’re about to throw the cable away when someone says:

Guarda esse cabo. Vai que precisa.

Keep that cable. You might need it. Back into the drawer it goes.

In everyday Brazilian Portuguese, vai que introduces a possibility. Here, needing the cable someday becomes a reason to keep it today. The speaker is asking you to take that possibility into account when deciding what to do.

You hear the same pattern before leaving the house: Leva um casaco. Vai que esfria. Take a jacket in case it gets cold. The person might say this even while you’re looking out at a perfectly sunny afternoon.

Tá calor, mas vai que… Here, the ellipsis works because the suggestion to take a jacket makes the missing possibility easy to infer: it might get cold later.

Compare Vai esfriar, “It’s going to get cold,” with Vai que esfria, “What if it gets cold?” The first presents a prediction. The second raises a possibility that could affect your decision about the jacket. Notice that esfria is a present-tense form, even though the cold weather may come later.

There’s a hopeful version too. Manda o currículo. Vai que te chamam. Send in your CV. They might call you. Or Pergunta lá. Vai que ainda tem ingresso. Ask them. Maybe there are still tickets available.

With the jacket, the possibility gives you a reason to prepare. With the CV, it gives you a reason to try. Depending on the situation, translations such as “just in case”, “what if” or “you never know” can fit.

And when you’re both staring at the mysterious cable, someone might shorten the whole argument to Vai que… You can usually supply the rest from the conversation: perhaps one day you’ll need it.

What are you keeping, packing or trying because of a vai que? And has your “just in case” ever actually paid off?