Fermentation is a metabolic process that converts sugar to acids, gases, or alcohol. It occurs in yeast and bacteria, and also in oxygen-starved muscle cells, as in the case of lactic acid fermentation.
pupil noun [C] (EYE PART). âº the âcircular âblack âarea in the âcentre of an âeye, through which âlight âenters: Pupils âcontract in âbright âlight, and âdilate in darkness. (Definition of pupil from the Cambridge Advanced Learners Dictionary & Thesaurus Â© Cambridge University Press).
It is surrounded by the iris, which is the colored part  of your eye.   The pupil allows light to enter the eye. â¦Light  enters through the pupil, passes through the lens, and is focused  onto the retina. The retina is the back part of the eye that has  the receptors that interpret what you see.