Fortified wines — including vermouth, sherry, port, and Lillet — are wines strengthened with a distilled spirit and used as essential modifiers that add vinous complexity, sweetness, and aromatic character to cocktails. Vermouth is the most iconic example, forming the backbone of the Martini and Manhattan, while sherry and port contribute rich, nutty, or fruity depth to more elaborate creations. Their relatively lower alcohol content and wine-derived nuance make them indispensable for building balanced, sophisticated drinks.