French for "juice," which can refer to both fruit and vegetable juices, as well as the natural juices exuded from meat. Jus de citron is "lemon juice," while jus de viande means "juices from meat." A dish (usually meat) that is served au jus is presented with its own natural juices.
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.