A herb (pronounced "hurb" in Commonwealth English and "urb" in American English) is a plant grown for culinary, medicinal, or in some cases even spiritual value. The green, leafy part of the plant is typically used. General usage differs between culinary herbs and medicinal herbs. A medicinal herb may be a shrub or other woody plant, whereas a culinary herb is a non-woody plant. By contrast, spices are the seeds, berries, bark, root, or other parts of the plant, even leaves in some cases; although any of these, as well as any edible fruits or vegetables, may be considered "herbs" in medicinal or spiritual use. Culinary herbs are distinguished from vegetables in that they are used in small amounts and provide flavor (are spices) rather than substance to food.

Botanical definitions

In botany, a herb is a plant that does not produce a woody stem, and in temperate climates usually dies, either completely (annual herb) or back to the roots (perennial herb), at the end of the growing season. Examples include bulbs, Peonies, Hosta, grasses and Banana [1].

The term herbaceous means either having the characteristic of a herb or being leaf-like in color and texture. A related term from American English is forb, which means a non-woody plant that is not a grass and is not grass-like. This means that the term forb excludes sedges (Cyperaceae) and rushes (Juncaceae) along with true grasses (Poaceae). Non-herbaceous plants are woody plants which have stems above ground that remain alive during winter and grow shoots the next year, such as trees, shrubs, and woody vines.

Cite: Wikipedia