This group has been named the Air Signs because each of these signs has a hot and wet nature, that are the fundamental "vapors" that constitute the Air Element. This group is well known for their mental acuity and social nature.
People born into this group tend to be charming conversationalists, inventive and spontaneous.
The Air Signs were originally known as the Libra Trigon. The three signs belonging to this Trigon are Libra, Aquarius and Gemini. These signs are part of the same Trigon because they are 120 degrees from one another; their images can be connected by straight lines, which then form an equilateral triangle.
Unless there is a strong preponderance of planets in signs of a different element at the time of birth, people born into the Element of Air tend to always be in motion, either physically or mentally. People born under Air Signs are known for their desire to be fair and seek the truth. They are seldom overly emotional, highly skilled, and usually careful in making decisions. All Air Signs need periods of rest in order to balance their intense periods of activity.
Every sign of the Zodiac has individual characteristics, as well as those which are shared by other members of the same elemental group. One of the ways astrologers distinguish them is through the Quadrature or Quality to which they belong.
Libra, being the Cardinal Sign of the group, wants to lead by bringing out the truth for others to follow. Because of this, a Libra person usually possesses a gift for logic, and an extremely gracious and charismatic nature that makes it nearly impossible to win an argument with them. They are quite social and take their time when coming to decisions.
Aquarius is the Fixed Sign of the group, and tend to be surprisingly set in their ways. Aquarians dislike conformity, and are very inventive. They often choose lifestyles that are unique or unconventional, and value friendship above all things. Aquarians often have altruistic motives, but tend to be a little insensitive emotionally.
Gemini is the Mutable Sign of the group, and almost always has the "gift of gab"; they are excellent storytellers and writers. Gemini folks seek variety in life, and become bored very easily. They tend to be experts at whatever they do, and are usually very flexible in their viewpoints on things. They tend to avoid commitments that limit their options, and tend to change their minds often.
The reverence with which the ancients viewed the pure or "Platonic" solids of Sacred Geometry is reflected in their assignment of natures and qualities to the Zodiac signs. Signs are considered to harmonize with one another when they belong to the same Trigon. It's generally expected of Libra to be a good match for Aquarius or Gemini, but the Elemental Trigons among the Zodiac Signs alone do not complete the full range of factors involved in astrological compatibility. The Zodiacal positions of the Moon and the planets at the time of birth, as well as the rising sign expand the possibilities of accord and discord among individuals almost infinitely.
Generally, Libra, Aquarius and Gemini tend to get along well. Libra may seem indecisive yet convincing at the same time, whereas Aquarians tend to enjoy surprises more than the other members of the group. Gemini is known for being distracted easily and changing their mind often. These are usually the aspects of their natures that clash with one another.
All three signs are mental in orientation, but they are so in very different ways. Gemini tends to work with the verbal and intellectual part of the mind, where Libra tends to rely on hairsplitting logic. Aquarians are more intuitive and tend to get the right answers because they ask the right questions.
Modern astrologers agree that Air Signs generally get along with Fire Signs, because the element of Fire is fed by Air. If we go back to the classical doctrine, the Air Signs are hot and wet, while the Fire Signs are hot and dry; they share the warmth, and are balanced by each other's moisture and dryness.
Basically, Libra, Aquarius and Gemini usually do well with Aries, Leo and Sagittarius. Even in this generalized elemental theme of the Zodiac signs we can find differences among the individual signs; Aries may not like waiting for Libra to make up its mind; Aquarius may not enjoy the bluntness of Sagittarius.
There is something to this general theory, however; the Air Signs are of the same nature, and share a part of their fundamental nature with the Fire Signs.