Herbs vs. Spices

Herbs and spices all come from plants, they do not all come from the same parts of plants. Herbs are the leaves of a plant—things like parsley, sage, rosemary, thyme, and others.

A seasoning harvested from any other part of the plant—including the roots, bark, seeds, rhizomes, bulbs, buds, etc.—is considered a spice. Cinnamon sticks are really bits of bark from trees in the Cinnamomum genus, while cloves are dried flower buds from the clove tree.
Some plants boast an herb and a spice. The leaves of the Coriandrum sativum plant are widely known as cilantro, which is definitely an herb. The seeds usually called coriander, are a spice, but cilantro and coriander are both common names for the whole plant, and cilantro is just the Spanish word for coriander. Dill is another example. Dill weed refers to dill leaves (the herb), while dill seed, which is actually not a seed, but the tiny, brown fruit of the dill plant is a spice.

According to Merriam-Webster, the botanical definition of herb is “a seed-producing annual, biennial, or perennial that does not develop persistent woody tissue, but dies down at the end of the growing season.” Botanically speaking, herbs are whole plants that do not have wooden parts like trees and bushes. The entire cumin plant, for instance, whose seeds are ground into a spice, is technically an herb.