Geminis are said to have a dual nature, as symbolized by twins. This duality also represents exchange and interaction. The sign of Gemini is closely associated with exchange of ideas, communication, and trade.
The sign of Gemini is thought to be very adaptable and flexible, sometimes to the point of "being" two different personalities.
The glyph for Gemini depicts two lines joined together, showing the symbolism of the twins, and the duality of the nature of the sign.