You will perhaps know that Spanish LOVES its subjunctive mood (used to express doubt, wish, some sort of counterfactual thought). Mostly its construction is easy: you just changing a vowel
- Cantas, you sing.
- Quiero que cantes, I want you to sing.
But some verbs have irregular subjunctives. Like “haber” (either the auxiliar “have” or “for something to exist”) which gives us the form “haya-”
Or [gasp!] “haiga-.”