• a leaf of a book: see recto and verso
• Folium of Descartes
  Folium of Descartes
  In geometry, the Folium of Descartes is an algebraic curve defined by the equationx^3 + y^3 - 3 a x y = 0 \,.It forms a loop in the first quadrant with a double point at the origin and asymptotex + y + a = 0 \,.It is symmetrical about y = x....
  
  , an algebraic curve

Botany

• Turnsole
  Turnsole
  Turnsole or folium was a dyestuff prepared from the annual plant Crozophora tinctoria .-History:...
  
   or folium, a dyestuff
• Folium Phyllostachydis, processed leaves of bamboo
• Hydrangeae Dulcis Folium, processed leaves of hydrangea