A spice is a seed, fruit, root, bark, berry, bud or other vegetable substance primarily used for flavoring, coloring or preserving food.
Spices are distinguished from herbs, which are parts of leafy green plants used for flavoring or as a garnish. Many spices have antimicrobial properties. This may explain why spices are more commonly used in warmer climates, which have more infectious diseases, and why the use of spices is prominent in meat, which is particularly susceptible to spoiling.
The spice trade developed throughout South Asia and Middle East by at least 2000 BCE with cinnamon and black pepper, and in East Asia with herbs and pepper.
The Egyptians used herbs for mummification and their demand for exotic spices and herbs helped stimulate world trade. The word spice comes from the Old French word espice, which became epice, and which came from the Latin root spec, the noun referring to “appearance, sort, kind”: species has the same root.
By 1000 BCE, medical systems based upon herbs could be found in China, Korea, and India. Early uses were connected with magic, medicine, religion, tradition, and preservation.
A spice may be available in several forms: fresh, whole dried, or pre-ground dried.
Generally, spices are dried. A whole dried spice has the longest shelf life, so it can be purchased and stored in larger amounts, making it cheaper on a per-serving basis. Some spices are not always available either fresh or whole, for example turmeric, and often must be purchased in ground form. Small seeds, such as fennel and mustard seeds, are often used both whole and in powder form.
Source: Thomas, Frédéric; Daoust, Simon P.; Raymond, Michel (2012). “Can we understand modern humans without considering pathogens?”. Evolutionary Applications, A Busy Cook’s Guide to Spices by Linda Murdock , Wikipedia