Capricorn vs Capricornus

Capricorn and Capricornus both are nouns.

Word	Noun	Adjective	Verb	Adverb
Capricorn	Yes	No	No	No
Capricornus	Yes	No	No	No

As nouns, Capricorn and Capricornus are synonyms defined as:

Capricorn and Capricornus: a faint zodiacal constellation in the Southern Hemisphere; between Sagittarius and Aquarius

Capricorn (noun)	Capricornus (noun)
the tenth sign of the zodiac; the sun is in this sign from about December 22 to January 19	a faint zodiacal constellation in the Southern Hemisphere; between Sagittarius and Aquarius
a faint zodiacal constellation in the Southern Hemisphere; between Sagittarius and Aquarius
(astrology) a person who is born while the sun is in Capricorn