What's the difference between 'ask' and 'inquire'? Can I use them interchangeably?
You can ask that someone perform an action.
When you inquire you only request information.
You can ask for permission, a favour, or forgiveness, but not inquire for them.
They're not interchangeable, ask is broader.
In the most basic form, ask can be applied to any question and the response may be completely ignored if not required. Inquire, on the other hand, implies an eagerness on the part of the former to receive a response.
In American and Australian English, they are interchangeable, but an inquiry would be a more formal investigation.