Definition of folium:
(n) :
A leaf (2 pages) of a codex or manuscript.
(n) :
A document that acts as the legal record of a transaction.
(n) :
(especially real estate) A certificate of title.
(n) :
(rare) A leaf.
(n) :
(anatomy) A lobe on a branching structure.
(n) :
A leaf-like protrusion or lobule on one of the vermes of the cerebellum.