part of fluid cline envoPolar A similar term exists in linguistics and mathematics. An ecocline, or biological cline, is a related concept; however, may be better placed as a child of a class like "ecotone". Further, some definitions of "layer" require a layer's constiuent materials to have consistent properties, thus "cline" would not qualify as a subclass. The term "gradient" has been proposed as a more suitable superclass. Discussion in Issue #286) A fluid front which is 1) thin in comparison to the fluid mass it is a part of and 2) across which a property of that fluid mass varies greatly over short vertical distance, relative to variation across the entire fluid mass. ORCID:0000-0002-4366-3088 cline 2013-10-06T20:10:13Z gaseous environmental material liquid environmental material fluid front