Many consumers and restaurants use the terms “shrimp” and “prawns” interchangeably. Terminology also varies from nation to nation, which can make matters even more confusing. In fact, shrimp and prawns are closely related, but there are a few distinguishing features which divide the two. Unfortunately for most consumers, these features are usually obscured in the harvesting and cooking process, so unless you have captured the crustaceans yourself, you may never know whether you are eating shrimp or prawns.

Starting with the similarities can help to highlight the differences between shrimp and prawns. Both are decapod crustaceans, meaning that they have exoskeletons and 10 legs. They can be found in salt and fresh water all over the world, typically swimming in search of food. Both shrimp and prawns tend to stay near the ocean floor. They also have similar flavors, and come in a wide range of sizes from minuscule to quite large.

Culinarily, many people distinguish between shrimp and prawns on the basis of size. “Prawns” are considered to be larger, while shrimp are smaller. In terms of biology, however, things get a bit more complex, since shrimp and prawns are in different suborders, indicating key biological differences between the two. Prawns are in the suborder Dendobranchiata, while shrimp are classified as Pleocyemata.

The primary difference is the gill structure. Shrimp have branching gills, while prawns have lameller gills with a platelike structure. There are a few other distinguishing features. The front pincers of shrimp are typically the largest, while prawns have bigger second pincers. Prawns also have longer legs than shrimp. These differences may seem subtle, but they indicate different steps along the evolutionary path of both creatures.

Numerous varieties of shrimp and prawns are harvested for consumption. Some common shrimp species include spot, pink, white, and brown shrimp, along with Northern shrimp. Prawns that you may find at the fishmonger include tiger, deep water, bay, and king prawns.

Conservation organizations urge consumers to use caution when purchasing prawns and shrimp, since many are caught and farmed in nations with lax environmental and fishing regulations. The United States in particular has made major changes in the legislation governing shrimp farming, in the hopes of making it more sustainable, so American farmed shrimp is a reasonable choice at the grocery store. Wild-caught Northern shrimp are also good buys, as are spot prawns.