Some of you may not be aware of the actual difference between an herb and a spice. Quite often many people use the two terms interchangeably.
Over time the definitions for herbs and spices have changed a bit. In the past, spices have been categorized as fragrant, aromatic plant products like cinnamon, cloves, ginger and pepper, while herbs have always been recognized as green, leafy plants like mint, rosemary and thyme.
Today, according to the American Spice Trade Association, spices have become known as "any dried plant product used primarily for seasoning purposes." This all-inclusive definition seems to cover a wide range of plants like herbs, spice seeds and even dehydrated vegetables and spice blends.
Here, then, complete definition from Horticulture and Home Pest News: Herbs and spices are obtained from plants. (Salt is neither a spice nor an herb. It is actually a mineral.) Herbs and spices are used primarily for adding flavor and aroma to food. And both are best used fresh but can be saved by drying. While there are similarities, there also are subtle differences between herbs and spices.
Herbs are obtained from the leaves of herbaceous (non-woody) plants. They are used for savory purposes in cooking and some have medicinal value. Herbs often are used in larger amounts than spices. Herbs originated from temperate climates such as Italy, France, and England. Herb also is a word used to define any herbaceous plant that dies down at the end of the growing season and may not refer to its culinary value at all.
Spices are obtained from roots, flowers, fruits, seeds or bark. Spices are native to warm tropical climates and can be woody or herbaceous plants. Spices often are more potent and stronger flavored than herbs; as a result they typically are used in smaller amounts. Some spices are used not only to add taste, but also as a preservative.
Some plants are both herbs and spices. The leaves of Coriandrum sativum are the source of cilantro (herb) while coriander (spice) is from the plant's seeds. Dill is another example. The seeds are a spice while dill weed is an herb derived from the plant's stems and leaves.