While opposite signs appear vastly different, on close study the similarities between opposite signs in astrology are pronounced. Opposite signs are those signs that are at the polar opposite end of themselves. Gemini and Sagittarius are one of them. Gemini is an air sign, while Sagittarius is a fire sign. Both signs are known to quest for knowledge, though the means of acquisition is different.
Gemini would love gaining knowledge from the intellectual direction, this includes reading books, attending lectures and participating in casual debates. Sagittarius on the other hand would love gaining knowledge via exploration. This includes: Travelling, understanding culture by observation, interacting with gurus, thinking philosophically about that which is puzzling. But on closer inspection, you will see that both Sagittarius and Gemini can share their opposite traits though it might be expressed differently. Sagittarius may appear as a lover of debates and a book worm while the Gemini might like to understand by observation and exploration.
Sagittarius are known to have good traits of being an humorous life of the party. Bad traits of Sagittarius would be self righteousness, double talk, (A common Gemini trait as well), insensitive, a religious fanatic (this comes from obsession with their believes). Gemini are also known as the fun talkative one, or the quite cool one. The bad traits include being two faced, indecisive, unstable in thought, insensitive, etc.
Though they are opposite signs, they have similar traits expressed in different ways. A Gemini being an air sign will have more propensity to be a more indoors kind of person than fire sign Sagittarius (ofcourse this depends on a person’s overall birth chart).