underside; undersurface; inferior surface
Refers to the bottom or lower surface of a physical object. Often used in technical or descriptive contexts. The antonym is 上面 (じょうめん, top surface).
See also: 上面
There was gum stuck to the underside of the desk.
There is a ventilation opening on the underside of this machine.
bottom fermentation
area under the curve; AUC
Compound of 下 (か, lower) and 面 (めん, surface). The reading かめん is a straightforward on'yomi combination.