Cumin is the dried seed of the herb Cuminum cyminum, a member of the parsley family. Cumin seeds which resemble caraway seeds, are oblong, ridged, and yellow-brown in color. Cumin seeds, known for their distinctive aroma, are popular in North African, Middle Eastern, Indian, Cuban and Northern Mexican cuisine.
Sold whole or ground, cumin seeds come in three colors: amber, white and black. Amber is most widely available, but black cumin has such a complex flavor it should not be substituted for the other two. No matter what color, these seed's characteristic flavor and aroma comes from their essential oil which benefits from a quick frying or dry roasting.
In some cases, you can use caraway seeds (but only use about half as much), or a mix of caraway and anise seeds. Amber cumin seeds may be substituted for white cumin seeds and vice versa.
Toasting the whole seeds briefly before grinding expresses essential oils and brings out flavor.
As with all spices, store cumin seeds away from light and heat and track their age by labeling purchase dates. Change your stock about every six months for ground spices and every year for whole spices. Spices don't go "bad," but as they age they will lose their potency.