What is an adjunct ingredient?

Adjunct is a bit of a moot word in the brewing industry, and refers to the use of a non-traditional ingredient outside the usual malted barley, hops, water and yeast. There are some adjuncts that are accepted as they relate to or innovate on a beer style – cherries in a Kriek or grapefruit in an American-hopped IPA for example. Other adjuncts such as corn or maize act as inexpensive substitutes for a primary ingredient. These are cheap shortcuts in brewing and are most of the time a way to minimise costs at the expense of quality, frequently producing off flavours and reducing the complexity of the beer.