Gemini vs Twins

Gemini and Twins both are nouns.

Word	Noun	Adjective	Verb	Adverb
Gemini	Yes	No	No	No
Twins	Yes	No	No	No

As nouns, Gemini and Twins are synonyms defined as:

Gemini and Twins: the third sign of the zodiac; the sun is in this sign from about May 21 to June 20

Other synonyms of Gemini include Gemini the Twins.

Gemini (noun)	Twins (noun)
the third sign of the zodiac; the sun is in this sign from about May 21 to June 20	the third sign of the zodiac; the sun is in this sign from about May 21 to June 20
a zodiacal constellation in the Northern Hemisphere between Taurus and Cancer on the ecliptic
(astrology) a person who is born while the sun is in Gemini