Pis·ces / ˈpīsēz/ 1. Astron. a large constellation (the Fish or Fishes), said to represent a pair of fish tied together by their tails. ∎  [as genitive] (Pis·ci·um / ˈpishēəm/ ) used with a preceding letter or numeral to designate a star in this constellation: the star Alpha Piscium.2. Astrol. the twelfth sign of the zodiac, which the sun enters about February 20. ∎  (a Pisces) (pl. same) a person born when the sun is in this sign.DERIVATIVES: Pis·ce·an / -sēən/ n. & adj. (in sense 2).

Pisces In some classifications, a superclass of the Gnathostomata (jawed chordates) comprising the fishes (compare Tetrapoda). The whole body of a fish is covered with a tough, usually scaly, skin (see scales), which extends over the eye and contains pigments and sometimes slime glands. The circulatory system is a single circuit with blood passing through two sets of capillaries, one at the gills and the other in the body tissues. Three semicircular canals are present in the inner ear. The sense of smell is particularly well developed and pressure waves are detected by the lateral-line system (see lateral-line canal). Fossils of fish date back to the Ordovician period, 505–438 million years ago. There are two classes of modern fish: Chondrichthyes (cartilaginous fishes) and Osteichthyes (bony fishes).

Pisces In older classifications, a superclass containing the four classes of fish: the two extant classes Chondrichthyes (cartilaginous fish, e.g. sharks) and Osteichthyes (bony fish), the extinct class Placodermi, and also the most primitive of the vertebrates of the class Cephalaspidomorphi. The first protofish are known from late Cambrian fossils, and the first true fish, an agnathan, has been recorded from earliest Ordovician sediments. Most modern classifications omit the term ’Pisces’, regarding it as artificial. See also GNATHOSTOMATA.

Pisces a large constellation (the Fish or Fishes), said to represent a pair of fishes tied together by their tails. In Astrology, the twelfth sign of the zodiac, which the sun enters about 20 February.

Pisces (the Fishes) Inconspicuous equatorial constellation situated on the ecliptic between Aquarius and Aries; it is the 12th sign of the Zodiac.