Capricornus vs Capricorn

Capricornus and Capricorn both are nouns.

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

As nouns, Capricornus and Capricorn are synonyms defined as:

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

Capricornus (noun)	Capricorn (noun)
a faint zodiacal constellation in the Southern Hemisphere; between Sagittarius and Aquarius	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
	(astrology) a person who is born while the sun is in Capricorn