The article does have definitions of both primary and common, though:

> By saying "primary", we aim to include names of dominant use, rather than having to add every conceivable local nickname or variation. By saying "common", we mean to include names which are in widespread daily use, rather than giving immediate recognition to any arbitrary governmental re-naming. In other words, if a ruler announced that henceforth the Pacific Ocean would be named after her mother, we would not add that placemark unless and until the name came into common usage.