A tamarind is a big tropical tree, and also the fruit it makes. The fruit is a brown pod, a bit like a fat curved bean, and inside is a soft dark-brown paste around some hard seeds. That paste is the useful part. It tastes sour first, then sweet behind the sour.

The word usually points at the food, not the tree. In cooking, tamarind is what gives that deep sour taste in Thai, Indian, Filipino and Mexican dishes — pad thai, Indian chutney, sinigang, and the sour tamarind sweets and drinks sold in Southeast Asia. You buy it as a sticky block, as paste in a jar, or as juice. If a recipe says "add tamarind", it almost always means the paste or the water made from it, not the tree and not the whole pod.

One small thing worth knowing: the sour taste is not lemon sour. Lemon is sharp and bright and disappears; tamarind is round and dark and stays in the mouth. Cooks pick tamarind exactly for that difference, so swapping in lemon juice changes the dish more than students expect.