An herb is a plant used to add flavor to food or to make medicine. When you sprinkle basil on pizza, stir cilantro into salsa, or smell the rosemary in roasted chicken, you're experiencing herbs. Unlike spices, which usually come from seeds, bark, or roots, herbs come from the leafy green parts of plants.

Cooks use herbs both fresh and dried. Fresh herbs like parsley or mint taste bright and lively, while dried herbs like oregano or thyme pack more concentrated flavor into a smaller amount. Some herbs, like dill or chives, taste best fresh. Others, like bay leaves, work better dried.

For thousands of years, people have also used herbs as medicine. Before modern drugs existed, healers brewed teas from herbs like chamomile to help people sleep or used peppermint to soothe upset stomachs. Today, many medicines still come from plants that were first used as herbs.

The word can also describe plants that die back completely each year, unlike woody plants like trees and shrubs that keep their stems through winter. A botanist might call a tomato plant an herbaceous plant because it grows, produces fruit, and dies all in one season.