Galangal (Alpinia galanga), also called greater galangal or Thai ginger, is the aromatic rhizome of a tall tropical herb in the ginger family — a close cousin of ginger but paler, firmer and far more fibrous, with a sharp, piney, citrus-and-pepper bite and a cool, almost medicinal eucalyptus note that ginger never has. It is a cornerstone of Southeast Asian cooking: sliced or pounded into the curry pastes of Thailand and Indonesia and into the sour, fragrant broths of tom yum and tom kha gai, where its terpene-driven aroma gives the dish its unmistakable lift. Greater galangal (A. galanga) is the common culinary species; a smaller, more pungent relative, lesser galangal (A. officinarum), is used mainly in southern China and in herbal medicine.