A d4 — also called a four-sided die, a caltrop (because of both their shape and how much they hurt if accidentally stepped upon) or, less commonly, a tetrahedron — is one of several standard polyhedral dice used in gaming. Each type is generally identified by the use of the letter "d" (for "die" or "dice") and the number of sides the die features. Multiple dice are connotated by an additional number prefixing the D. So rolling five four-sided dice would be noted by writing 5d4.
Because of its shape, the d4 doesn't have an "up" face like all other types of die. As a result, two variants of d4s have arisen to try to solve this problem. The first type (above right) displays the result in the corner, such that the result of a roll is always the uppermost number.
The second d4 variant (bottom right) displays the result along the edge, such that a roll's result is always the number closest to the table.
Dice Used in Roleplaying Games