I'm of the opinion we made up all the words, but those mouth sounds must have a strict meaning whenever possible. Words are important, they're how you communicate concepts. Everyone should be precise with their words to the best of their understanding, if you have to redefine the word planet in every conversation the concept is diluted and you waste a lot of time

In this case, if Pluto is a planet, we have at least 13. We might discover another 10 or 20 if there's no planet 9 hiding behind the kyper belt and it's all dwarf planets... Ain't no one got time to remember 30+ planets