fluorescence. Power of a body to change wave-rate (or color) of light passing through it.

focus. Point at which light rays meet. The starting point of a disease process.

follicle. A small secretory cavity or sac.

form. Shape, as in vermiform, resembling a worm in shape.

formaldehyde. A gas possessing powerful disinfectant properties.

fracture. A break, as of a bone.

fulcrum. The point against which lever is placed to get purchase.

fungating. Rapidly growing (path.).

fungus (plural fungi). A cellular vegetable organism which feeds on organic matter. Example, bacteria.

furunculosis. The systemic condition marked by boil-formation.