A herb is a plant that is valued for flavour, scent, or other qualities. Culinary use of the term "herb" typically distinguishes between herbs, from the leafy green parts of a plant, and spices, from other parts of the plant, including seeds, berries, bark, root, fruit, and even occasionally dried leaves or roots. Culinary herbs are distinguished from vegetables in that, like spices, they are used in small amounts and provide flavour rather than substance to food.

Some culinary herbs are shrubs (such as rosemary), or trees (such as bay laurel) – this contrasts with botanical herbs, which by definition cannot be woody plants. Some plants are used as both a spice and an herb, such as dill seed and dill weed or coriander seeds and coriander leaves.