Of course, there are some definitions that reference themselves that are not circular, or alternatively, some circular definitions that are useful. For example, the definition of "ancestors" might be "your parents and your parents' ancestors" (with the implication that if you don't exist, you don't have any ancestors). But I agree that this is not a useful definition for "tensor".
Do you really need me to explain the distinction between "circular" and "recursive", and the nature of HN comments as an informal medium with an audience that generally does understand these things and does not need to have them explicitly called out?
