estuary (es'-tu-a''-ry). A semi-enclosed coastal body of water that has a free connection with the open sea and within which seawater is measurably diluted with freshwater from land drainage (Pritchard, 1952). Estuaries are classified in terms of their mixing as stratified, partially stratified, well mixed, and reverse; or by their origins as bar-built, fjord, tectonic, fjard, and ria (Woodroffe, 2002). Cf: ria; branching bay; liman; fjord. Etymol: Latin aestus, "tide".