A crown prince, hereditary prince, or dauphin, was an aristocratic title generally reserved for the eldest son of the King, a prince, who was first in line of succession in a monarchy, making him the heir apparent.
In 2269, Garth suggested to James T. Kirk he could become his crown prince and thus heir apparent for Garth's self-appointed position as master of the universe. (TOS: "Whom Gods Destroy")
In 2374, Hain falsely told Quark that Morn had been the crown prince of the Royal Family of Luria. (DS9: "Who Mourns for Morn?")
A creature]identified by Mariner as a "dauphin"
In 2380, Ensign Beckett Mariner used the term allegorically to describe allasomorphs, as represented by Salia (the predetermined head of state of Daled IV) and Anya (her governess), the only two representatives of their species known to the Federation. That year, when Mariner was attempting to determine Lieutenant Barbara Brinson's true nature (which turned out to be Human), she initially had a photograph of what was actually the form taken by Anya, the "dauphin's" governess, on her conspiracy board. Though aware of their shape-shifting abilities, Mariner quickly convinced herself that "Barb's not a dauphin." (LD: "Cupid's Errant Arrow")