Basil is an annual herbaceous plant in the mint family Lamiaceae. It has square stems with leaves that grow on opposite sides, and the leaves are rounded, slightly cupped, and curve to form at point at the tip. The leaves are generally light green, although some varieties have reddish or purplish leaves. The stems can grow to between 12 and 50 inches high (30.5 to 125 centimeters), depending on variety and conditions.

The flowers are small, usually white in color and arranged along a spike that grows from the tip of the stem. After pollination, the flower falls off and four round, dry structures called achenes develop, each one containing a seed. The seeds are small, dark, and edible.