Distilled herbs (like cinnamon and nutmeg), roots and, sometimes, tree bark, that are called on in a number of cocktail recipes like the Old fashioned or a basic martini. Some people drink bitters over ice and with a little water as you would a pastis. Variations and producers abound, like the Italian Fernet-Branca and Campari or the Danish Gammel Dansk.

Generally when called for in a cocktail recipie, the intent is for Angostura Bitters. Angostura is the most widely used and available bitters in the U.S.

Some suggest that one cannot make a proper martini without Orange Bitters, which has recently been having a resurgence of availability in America.

If you hail from New Orleans, you already know about Peychaud’s Bitters, which are critical for making a Sazerac.

In mixology bitters are not interchangable.