A clam is a bivalve mollusk. The word "clam" has no real taxonomic significance in biology. However in the United States the word can sometimes be used to mean any bivalve mollusk. It more properly refers to a bivalve other than an oyster, mussel, or scallop, and that has a more-and-less oval shape, or a freshwater mussel. The word clam is also very often used to mean any one of many edible bivalve species which live buried in mud or sand and communicates to the water by means of a siphon, hen… (More on Clam)