Wikipedia defines spice as "A spice is a dried seed, fruit, root, bark, leaf, or vegetative substance used in nutritionally insignificant quantities as a food additive for the purpose of flavour, colour, or as a preservative that kills harmful bacteria or prevents their growth.
"... In the kitchen, spices are distinguished from herbs, which are leafy, green plant parts used for flavouring purposes. Herbs, such as basil or oregano, may be used fresh, and are commonly chopped into smaller pieces. Spices, however, are dried and often ground or grated into a powder. Small seeds, such as fennel and mustard seeds, are used both whole and in powder form."