acaso

adv. perhaps

n. chance, accident

= at all.
Ex: Students who slight preclass preparation are a drag on the class; they will not know what is going on and if they speak at all will frequently attempt to wrest the discussion away from the case to more comfortable topics.
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* por si acaso = in case of, on the off chance, just in case.
* si acaso = if ever, if at all.