In pursuit of shrimp cookery, and especially shrimp, you'll usually run into two market terms whose meanings are not perfectly clear -- or, in the case of prawns, whose meanings are numerous and even contradictory.

Prawns may or may not be shrimp at all, though the name usually implies something larger than the norm. "Prawn" often describes a member of the lobster family, including such familiar seafoods as the French langoustine and the so-called Florida or Caribbean lobster. Some zealots claim these are better than Maine lobster or anybody's shrimp, relishing the tail meat -- a good idea, because there's little to nothing stashed in the small claws. Three other meanings of "prawn" do point toward shrimp, however. The word could mean any shrimp taken from fresh water (where some migrate from salt water to spawn in the manner of salmon), any shrimp farm-raised in fresh water (such as the chef-revered Hawaiian blue prawn), or perhaps just any shrimp from any type of water that strikes somebody as a Great Big One.

The other potentially confusing term is rock shrimp. They're also moving beyond restaurant novelty, most often connected with Florida but available in very deep waters across the Gulf of Mexico. Shrimpers started pulling these up as a by-catch in the 1960s but figured people wouldn't be able to crack the rock-hard shell. Once a gadget was invented to do just that, the marketing push was on. Rock shrimp, which once fed only shrimping families unable to sell them, are now all over menus. They're sold in markets without shells but vary wildly in availability and price. Florida, for instance, has recorded years of 3 million-pound catches and those with 23 million pounds -- with no explanation beyond that's how much they caught. And ate, probably.