A Jack or Knave, in some games referred to as a Bower, in Tarot card games as a Valet, is a playing card which, in traditional French and English decks, pictures a man in the traditional or historic aristocratic or courtier dress, generally associated with Europe of the 16th or 17th century. The usual rank of a jack is between the ten and the queen.

A playing card is a piece of specially prepared card stock, heavy paper, thin cardboard, plastic-coated paper, cotton-paper blend, or thin plastic that is marked with distinguishing motifs. Often the front (face) and back of each card has a finish to make handling easier. They are most commonly used for playing card games, and are also used in magic tricks, cardistry, card throwing, and card houses; cards may also be collected. Playing cards are typically palm-sized for convenient handling, and usually are sold together in a set as a deck of cards or pack of cards.