terrestrial planet vs planet

terrestrial planet and planet both are nouns.

Word	Noun	Adjective	Verb	Adverb
terrestrial planet	Yes	No	No	No
planet	Yes	No	No	No

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

terrestrial planet: a planet having a compact rocky surface like the Earth's; the four innermost planets in the solar system
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 terrestrial planet include major planet.

terrestrial planet (noun)	planet (noun)
a planet having a compact rocky surface like the Earth's; the four innermost planets in the solar system	(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
	any celestial body (other than comets or satellites) that revolves around a star
	a person who follows or serves another