It depends on the particular circumstance. In the continent of orgin, a ground segement is considered a stopover (unless you depart from the second city within 24 hours of arriving in the first city.) For example, I am flying CAI-MAD//LHR-HKG. the MAD-LHR is part of a seperate ticket. However, if I do not leave LHR for HKG within 24 hours of arriving in MAD, then it is considered a stopover. Stopovers only matter in the continent of origin (as far as I can tell).