A
chemical substance added to
food usually to
simulate a
natural flavor. Artificial flavors are used when they are
cheaper than
natural flavors, or easier to
produce. For instance, for
artifical fruit flavors like
grape, you can
synthesize them in a
lab and they're the same each time, and not dependent on the
harvest or the
growing conditions of the grapes.
Usually artificial flavors mimic the one or two most significant compounds of the natural flavor. The result is something which is almost, but not quite, the original flavor of whatever you're trying to imitate. The extreme is some candies or gums which are, say "berry flavored" without getting specific about what berries, exactly, they're supposed to taste like.
Artificial flavors are linked to hyperactivity in children by some--hence the Feingold diet. They just make me nauseous with few exceptions (those are citrus flavors and cinnamon in small amounts.)