Por si acaso

Question

I don't see how you know from the 'in case you forget' sentence whether it is likely or not. Surely it depends on whom you are talking to?

e.g. my daughter, not likely to forget; my husband, very likely to forget. How can I tell from the question?

Silvia Piriz · Accepted Answer

Hola Jill T.
Great question! In Spanish, "por si acaso" (or just "por si") can be used regardless of the likelihood of an event happening—it expresses precaution rather than probability.
You're right that context matters, but in general:
1. If something is unlikely, "por si acaso" can be translated as 'just in case' (e.g., Llévate un paraguas por si acaso llueve → 'Take an umbrella just in case it rains').
2. If something is likely, "por si" can still be used, but it often implies the speaker expects it might happen (e.g., Te dejo una nota por si llegas tarde → 'I'll leave you a note in case you arrive late').
Unlike English, Spanish doesn’t explicitly differentiate whether an event is likely or unlikely—"por si acaso" always works as a precautionary measure. So, whether you say it to your husband or daughter, it doesn’t change the structure of the sentence—just the pragmatic implication in the conversation.
Hope this helps!
Saludos
Silvia