(organic chemistry) Any amino derivative of levulinic acid, but especially 5-aminolevulinic acid which is an intermediate in the biosynthesis of porphyrin

plural of allegory

Someone who helps or facilitates; an assistant, a helper. [from 16th c.] / (medicine) Something that enhances the effectiveness of a medical treatment; a supplementary treatment. [from 18th c.]

To tick, buzz or become marked to indicate the passage of time.