facies

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

• noun Biology The general aspect or outward appearance, as of a given growth of flora.
• noun Medicine The appearance or expression of the face, especially when typical of a certain disorder or disease.
• noun Geology A rock or stratified body distinguished from others by its appearance or composition.

from The Century Dictionary.

• noun The face; specifically, in anatomy, the facial part of the skull or of the head.
• noun Features, visage, countenance, or physiognomy.
• noun Hence The whole outside figure; the general configuration.
• noun Hence The general aspect or appearance of anything; superficial characteristics or features; specifically, the general aspect which an organism presents at the first view, before the details have been considered separately: as, the facies of a country; the facies of a fauna.
• noun Specifically — In geology, the entirety of the lithologic and paleontologic characteristics resulting from the external conditions which determine the existence of any particular fauna or flora for a given region. These characteristics are defined by physical conditions, such as climate, altitude, or bathymetry, and the geological or chemical nature of the medium.
• noun In phytogeography, the physiognomy or characteristic appearance of a vegetation, depending upon the one or several species which predominate in it; or, the characteristic growth itself. A plant formation has one facies when there is one controlling species, and several when there are several such. See character-plant.
• noun In petrography, the different modifications of one mass of igneous rocks, distinguished by their texture, or by their mineral or chemical composition: as, granitic and porphyritic facies of a dike: a gabbro facies of a diorite mass.

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

• noun The anterior part of the head; the face.
• noun (Biol.) The general aspect or habit of a species, or group of species, esp. with reference to its adaptation to its environment.
• noun (Zoöl.) The face of a bird, or the front of the head, excluding the bill.
• noun (Med.) See Hippocratic.

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

• noun plurale tantum Appearance.
• noun plurale tantum, medicine Facial features, like an expression or complexion, typical for patients having certain diseases or conditions (e.g. costive facies).
• noun geology A body of rock with specified characteristics reflecting the way it was formed.