si
/si/ · A1 · conj
if, whether
From Latin si (if); no accent = if, with accent sí = yes
Spanish si comes straight from Latin si, meaning if. It sounds like English see: si llueve = see whether it rains. The accent mark is the only thing separating si (if, whether) from sí (yes). Also opens protests: ¡Si ya lo sabes! = But you already know!