Lentoid is a geometric shape of a three-dimensional body, best described as a circle viewed from one direction and a convex lens viewed from every orthogonal direction. It has no strict mathematical definition, but may be described as the volume enclosed within overlapping paraboloids.
Since ancient times, the lentoid shape has been used to fashion jewelry and seals for identification made from a variety of gemstones and metals. In Minoan Crete, for example, seals have been found with complex carving on lentoid stones. The lentoid shape was one of the most commonly recovered seal shapes from Minoan Knossos on Crete dating to the Bronze Age, as evidenced by the finds at that Bronze Age palace.