The act of something becoming darker.

present participle of darken

plural of darkening

(transitive) To make dark or darker by reducing light. / (intransitive) To become dark or darker (having less light).

Made dark or lightproof by the exclusion of light. / Having an absence of light, such as at night-time.

simple past tense and past participle of darken

Third-person singular simple present indicative form of darken

plural of darkener

One who or that which darkens.

(physics, astronomy) The phenomenon of a star rotating so rapidly that it is oblate, with a larger radius and thus lower surface gravity at the equator (which is thus cooler and darker: gravity-darkened), and higher surface gravity at the poles (which are hotter and brighter: gravity brightened).