Gastrique

Agrodolce (pronounced "agro-dolchay") is an Italian term for any sweet and sour sauce made with vinegar and sugar. A traditional version of this ages-old sauce would be similar to a French gastrique, containing nothing more than vinegar, wine, and sugar — although butter, dried fruit, and nuts may be added. The sauce lends a mouthwatering pucker to everything from sautéed vegetables like onions to proteins such as pork chops, meaty fish, and ground beef.

Source: Flickr User thebittenword.com

A thick sauce in classic French cuisine that consists of a reduction of vinegar, wine, sugar, and sometimes fruit that has been caramelized over heat.

A gastrique is employed to round out flavors in a dish, and is either served with meat or seafood, or used as a base for other sauces, such as one with tomatoes.

It can also be used to add complexity to fruit-forward cocktails.

Source: Flickr User finna dat