It is also considered a water sign and one of the four mutable signs. Pisces has been traditionally ruled by the planet Jupiter, but since its discovery, Neptune has been considered a modern ruler of this sign. Being the twelfth sign, Pisces is associated with the astrological twelfth house.
Individuals born when the Sun was in this sign are considered Pisceans. Under the tropical zodiac, the Sun is in Pisces roughly from February 19 to March 20, ending on the moment of vernal equinox by definition. In western astrology this sign is no longer aligned with the constellation because of the precession of the equinoxes. Under the sidereal zodiac, it is currently there roughly from March 15 to April 18.
Zodiac Symbol: Fish
Duration (Tropical, Western): 19 February – 20 March (2011, UTC)
Duration (Sidereal, Hindu): 14 March – 1 April (2011, UTC)
Zodiac Element: Water
Zodiac Quality: Mutable
Domicile: Neptune (day), Jupiter (night)
According to one Greek myth, Pisces represents the fish into which Aphrodite and her son Eros transformed in order to escape the monster Typhon; they are tied together with a cord on their tails, to make sure they do not lose one another. Alternatively, the twin fish were placed in the heavens in honor of their heroic deed of saving Aphrodite and Eros from Typhon on the river Euphrates.
Generally, the natives of Pisces are considered to be compatible with the natives of the other water signs, Scorpio and Cancer, and the natives of the earth signs, Taurus, Virgo and Capricorn. Gemini and Sagittarius are signs of the other nature (masculine/extroverted), but are considered semi-compatible with Pisces due to them having the same mutable quality.
There are many variables that determine compatibility in astrology, such as birth dates, birth months, birth years, position of a sign within the Sun, the Moon, Stars, etc. The signs listed as compatible with Pisces do not reflect an ‘individual profile’ or individual reading as interpreted within astrology, but rather reflect a general guideline and reference to compatibility as dictated by variables such as Qualities and Elements within the Zodiac. The branch of astrology dealing with interpersonal compatibilities is called Synastry.
Definition courtesy Wikipedia.