basil, any plant of the genus Ocimum, tender herbs or small shrubs of the family Labiatae (mint family), mostly of Old World warm regions and cultivated for the aromatic leaves. The basil of Keats's "Isabella" (and of Boccaccio's story) is the common or sweet basil (O. basilicum), once considered medicinal. This is the species usually used for seasoning; it is grown commercially chiefly in the Mediterranean area. There are also the holy basil, venerated in India; the bush basil; and related plants sometimes called basil. Basil is classified in the division Magnoliophyta, class Magnoliopsida, order Lamiales, family Labiatae.