ˈkambēəm noun
( plural cambiums -ēəmz ; or cam·bia -ēə)
Etymology: New Latin, from Medieval Latin, exchange, from Latin cambiare to exchange — more at change
: a formative layer one cell thick occurring between the xylem and phloem of most vascular plants, being persistently capable of giving rise to new cells, often for many years in woody plants, and being responsible for secondary growth — compare meristem , phellogen