Judo's kind of an interesting case, in that most of what calls itself "judo" in the modern day comes from a single lineage of Japanese grappling that was designed as a competitive martial art. The scope of Japanese grappling arts is much broader, and includes several less competitive and more self-defense oriented styles that could accurately have been called judo, but the Kodokan lineage has come to so dominate the field that anything not related to it now uses a different name (usually some form of "jujutsu"), to avoid confusion.