Phosphorus vs major planet

Phosphorus and major planet both are nouns.

Word	Noun	Adjective	Verb	Adverb
Phosphorus	Yes	No	No	No
major planet	Yes	No	No	No

As nouns, major planet is a hypernym of Phosphorus; that is, major planet is a word with a broader meaning than Phosphorus:

Phosphorus: a planet (usually Venus) seen just before sunrise in the eastern sky
major planet: (astronomy) any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun; viewed from the constellation Hercules, all the planets rotate around the sun in a counterclockwise direction

Other hypernyms of Phosphorus include planet.

Phosphorus (noun)	major planet (noun)
a planet (usually Venus) seen just before sunrise in the eastern sky	(astronomy) any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun; viewed from the constellation Hercules, all the planets rotate around the sun in a counterclockwise direction