Originally, the word 'planet' comes from the Greek word, wanderer/planetes from which the word, planet came from. Originally, the 'round' word wasn't involved at all.... originally. Unfortunately, if you go by the original Greek thought, everything/all matter that revolves around our sun is a 'wonderer'/planet.

I understand where you've been going on this. Even if Pluto is a cast off of the Kuiper Belt, it IS wondering (if I may) on it's own and was NOT captured by our gas giants, therefore it should be classified as a 'planet'.

What IS interesting about Pluto from the 'other' planets is that it is yet to be determined if it is terrestrial in nature. It is certainly not a gaseous planet and it seems to have friends (casts off from the Kuiper Belt and then there's that darn Oort Cloud).

Solar System:

G2 Type Star

Terrestrial Planets (and Earth's moon.)

Asteroid belt (asteroids and many captured moons).

Gaseous Planets (and possible moons with atmosphere... possibly. There's another debate.)

Kuiper Belt Objects (theoretically, could be active or spent comets)

Oort Cloud (theoretically, it is there and is made up of comets)

They're just having a hard time as to what type of planet Pluto is. I know, I (MMHO) think it's a KBO.

What of Sedna?

[Since the object appears to be somewhat smaller than Pluto and has an extremely elongated orbit with a period of around 10,000 years, compared to 248 years for Pluto, it seems appropriate to designate the object as an asteroid and not as the 10th planet.]

It seems logical that Sedna would have an even more elongated orbit around our sun than Pluto since it's much farther away (86 AU/TWICE Pluto's distance). How can they determine that Sedna is an asteroid when just about nothing about Sedna is known except for it just being there reflecting our sun's light? An elongated orbit? How do they know it's not 'round'. (I see your points, Mark.)

More here.