The first group is known as the cardinal signs, whose solar seasons coincide with the start of the four seasons of the year (Aries, Cancer, Libra, and Capricorn). Last week, for instance, you may have noticed that summer officially started right around the same time that your Twitter feed filled up with Cancer memes — that's because Cancer's solar season kicks off on the same day as the summer solstice. The second group is the fixed signs, whose solar seasons occur midway through their respective seasons (Taurus, Leo, Scorpio, and Aquarius). And the third is the mutable signs and they come at the end of spring, summer, fall, and winter (Gemini, Virgo, Sagittarius, and Pisces). The three modalities are similar to a sign's ruling planet or element in the sense that they give us a better understanding of its behaviourr.