In the JSend specification, what is the difference between a fail and an error?

According to https://labs.omniti.com/labs/jsend,

  • Fail: When an API call is rejected due to invalid data or call conditions
  • Error: When an API call fails due to an error on the server

Can this be interpreted as 4xx errors (such as a 404) should always return a Fail, but 5xx errors always correspond to a Error?