Why is question spelled with tion and not sion?

The word "question" is spelled with "tion" because it comes from the Latin word "quaestio," which means "inquiry" or "investigation."

The ending "-tion" is a common suffix in English, derived from the Latin "-tio," which is used to form nouns from verbs. It signifies the process of doing something or the result of an action.

The ending "-sion" is also derived from Latin, but it is used to form nouns from verbs that have a different stem than the Latin "-tio" verbs. For example, "permission" comes from the Latin "permissio."

So, because "question" is derived from the Latin "quaestio" which uses the "-tio" stem, it is spelled with "-tion."