上京 jōkyō is less a regular word and more a form of written shorthand. It would not be used in speech, and even in writing it's ambiguous: not only does 京 kyō simply mean "capital", but there's a district of Kyoto that's also 上京, only read Kamigyō.
The closest English equivalent is abbreviations like "PC". They're perfectly usable in context, but if you see one standing alone it's not clear if it's personal computer, politically correct, Peace Corps, etc etc.
The closest English equivalent is abbreviations like "PC". They're perfectly usable in context, but if you see one standing alone it's not clear if it's personal computer, politically correct, Peace Corps, etc etc.