A recently proposed meaning of pedoderm is more formally defined so as to contrast it with an older definition that is used infrequently in soil stratigraphy.. It is defined here as the thin layer of soil at the interface with the atmosphere, a few millimetres to centimetres thick, within which certain properties may exhibit a marked vertical change in expression sometimes not readily detected through field observation. The function of this generic term is primarily to draw attention to the variation of soil surface characteristics on a micro-scale that might otherwise be overlooked. It has implications for understanding material fluxes and ecosystem function and the use of remote sensing for soil evaluation. (c) 2005 Elsevier B.V. All rights reserved.