Pk is a written short form of park — the green public place, or sometimes the park in a name (Hyde Pk, car pk on an old map). You see it where space is tight: maps, street signs, timetables, addresses, notes. You would not usually say “Pk” out loud instead of park; it is a thing for the page. It is also easy to mix up, because PK in other worlds means very different things — though actually this entry is only the park one. In games, Taiwanese students often meet PK as “player kill” or a versus match; that is a different abbreviation that just happens to use the same letters. Capitalisation varies (Pk, PK, pk) depending on the map or the house style.