[医] 叶

[ noun ]
a thin layer or stratum of (especially metamorphic) rock
<noun.object>

Folium \Fo"li*um\, n.; pl. E. {Foliums}, L. {Folia}. [L., a
leaf.]
1. A leaf, esp. a thin leaf or plate.

2. (Geom.) A curve of the third order, consisting of two
infinite branches, which have a common asymptote. The
curve has a double point, and a leaf-shaped loop; whence
the name. Its equation is x^{3} + y^{3} = axy.