What makes a fox a fox?

Answer 1

This is a rather unclear question.

A fox is a fox (as in 'not a dog, wolf, coyote, or jackal') because of it's skeletal structure. Foxes are built smaller and their muzzles are very pointed as compared to other canids.

Other things that make the fox different from other canids are that foxes (depending on the breed) have very large ears, on their pads (of the paws) there is a raised and inverted 'V' shape that shows in the paw print, the dew-claws of the fox are much lower on the legs and also appear in a paw print, and the tail is long and bushy, as opposed to other canids that have smaller ears, rounded paws, higher dew-claws, and not-so-bushy tails.