plural of actin

(medicine, pathology, dermatology) A potentially precancerous skin lesion, typically on the upper portion of the head, characterized by discolored, thickened or scaly growths of keratin and caused by repeated exposure to ultraviolet light, such as from sunlight or tanning beds.

plural of actinic keratosis

The light available at a point in the atmosphere, especially that available to produce photochemical processes

A radioactive, metallic chemical element (symbol: Ac) with an atomic number of 89; found in uranium ores.

Temporarily assuming the duties or authority of another person when they are unable to do their job.

present participle of act

(countable, obsolete) An action or deed. / (law) Something done by a party — so called to avoid confusion with the legal senses of deed and action. / Pretending. / (drama) The occupation of an actor.

(of a gay or bisexual man (or, rarely, of a lesbian), potentially offensive) Having the appearance, mannerisms, etc., of a stereotypical heterosexual of the same gender rather than those stereotypically associated with gay men or lesbians.

(biochemistry) A protein-digesting enzyme present in kiwi fruit. It is also an allergen.