mutability in life or nature (especially successive alternation from one condition to another)
a variation in circumstances or fortune at different times in your life or in the development of something; "the project was subject to the usual vicissitudes of exploratory research"
the position of greatest importance or advancement; the leading position in any movement or field; "the Cotswolds were once at the forefront of woollen manufacturing in England"; "the idea of motion was always to the forefront of his mind and central to his philosophy"
having a play of lustrous rainbow-like colors; "an iridescent oil slick"; "nacreous (or pearlescent) clouds looking like mother-of-pearl"; "a milky opalescent (or opaline) luster"