Astrology divides the twelve signs into two polarities. Yin is the inward-moving half. It includes the Earth signs, Taurus, Virgo and Capricorn, and the Water signs, Cancer, Scorpio and Pisces. Counting from Aries, these are the even-numbered signs, so Yin and its partner Yang alternate all the way around the zodiac.
As a symbol, Yin describes energy that draws in, holds and consolidates. It takes in experience before responding, builds things that last, and tends to influence through presence, care and steady effort rather than announcement. Think of a friend who says little during the argument but quietly turns up the next day with exactly what you needed. That is the Yin move.
Older texts call these signs feminine and nocturnal (belonging to the night). Those are technical labels from a system that sorted everything into paired opposites, like odd and even or day and night. They say nothing about gender: a man with a Yin-heavy chart is not "feminine," and a woman with a Yang-heavy chart is not "masculine." Receptive does not mean passive, either. Yin is active in its own way: it gathers, protects, digests and builds.