stratification

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Formation or deposition of layers, as of rock or sediments.
• noun The condition of being stratified.
• noun A layered configuration.

from The Century Dictionary.

• noun The act of stratifying, or the state of being stratified; formation or arrangement in layers.
• noun Specifically, in geology, deposition in beds or strata: the mode of occurrence of those rocks which have been laid down or spread over the surface by water.
• noun In physiology, the thickening of a cell-wall by the deposition of successive thin layers of formed material; also, the arrangement of the layers so deposited.
• noun In electricity, the appearance presented by an electric discharge, or a series of rapid discharges, in a rarefied gas, light and dark bands or striæ being produced.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act or process of laying in strata, or the state of being laid in the form of strata, or layers.
• noun (Physiol.) The deposition of material in successive layers in the growth of a cell wall, thus giving rise to a stratified appearance.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun the process leading to the formation or deposition of layers, especially of sedimentary rocks
• noun music a layering of musical texture
• noun ecology the vertical layering of vegetation in a forest

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a layered configuration
• noun the placing of seeds in damp sand or sawdust or peat moss in order to preserve them or promote germination
• noun forming or depositing in layers
• noun the act or process or arranging persons into classes or social strata
• noun the condition of being arranged in social strata or classes within a group