Depending on the animal, the loin comes from the area on both sides of the backbone extending from the shoulder to the leg (for pork) or from the rib to the leg (in beef, lamb and veal). Beef loin is divided into short loin and sirloin. In general, the loin is a tender cut that can be butchered into chops, steaks and roasts.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.