sí
/ˈsi/ · A1 · pron
yes
✅ sí sounds like see: I see, yes — the accent mark separates it from si (if)
Sí comes from Latin sic (thus, so): saying yes was saying it is so. The written accent is the only thing that tells it apart from si, meaning if. The same accented form is also the pronoun after a preposition, as in para sí (for oneself).