What is ultra wealthy net worth?

Could you please explain what the term "ultra wealthy" actually means in terms of net worth? I'm interested in understanding the financial threshold that separates the merely wealthy from those who are considered ultra wealthy. Could you provide a general range or estimation of the net worth required to be considered ultra wealthy? Additionally, how does this definition vary across different countries or cultural contexts? I'm curious to know if there are any specific criteria or qualifications that need to be met in order to be categorized as ultra wealthy. Thank you for your assistance in clarifying this concept.