To form questions that elicit yes/no reponses, place the particle "ka" or "kad" at the beginning of a sentence.
- Ka Sean iris a la skolo? Did Sean go to school?
- Kad el perdis la pekunio? Did she lose the money?
Simple questions may be formed by placing "Ka" in front of a noun without a verb. Ka Michelle? can mean "Is it Michelle?" or "Do you mean Michelle?", depending on the context.
If there is a word like who, what, where, etc., ka/kad is not used:
- Ube vu habitas? Where do you live?
- Quo es filozofio? What is philosophy?
- Quon vu timas? What do you fear?
- Qua es la prezidanto? Who is the president?
- Quante vu evas? How old are you?