[for.ma.tion] n (15c) 1: an act of giving form or shape to something or of taking form: development
2: something that is formed "new word ~s"
3: the manner in which a thing is formed: structure "the peculiar ~ of the heart"
4: the largest unit in an ecological community comprising two or more associations and their precursors "grassland ~"
5. a: any igneous, sedimentary, or metamorphic rock represented as a unit b: any sedimentary bed or consecutive series of beds sufficiently homogeneous or distinctive to be a unit
6: an arrangement of a body or group of persons or things in some prescribed manner or for a particular purpose