Ro is an a priori artificial language created by Rev. Edward Powell Foster. In Ro, words are constructed using a catagory system. For example, to say red, you'd say 'bofoc', and yellow would be 'bofof'. "Bofo-" is the category of colors. Foster did not simply think "how could I make a better language", rather it came from a simple question he had. Foster wrote about Ro:
A common criticism of Ro is that it can be difficult to hear the difference between two words; usually one consonant makes the word completely different. That may have been why Ro didn't catch on as well as other contructed languages, such as Esperanto, even though esperanto was created later.