Three common substitutes for cumin are chili powder, ground coriander or caraway seeds. Use half the amount called for by the recipe, stir it in, then taste and add more, if necessary. If both are available, try using chili powder mixed with ground caraway seeds.
Experiment with different blends of the three spices until the desired taste is found.
Cumin is made from the small, dried fruit of a plant related to parsley. It is often confused with caraway but is hotter in taste. It originated in the region from the Mediterranean Sea through to India and is used frequently in Indian, Middle Eastern, Mediterranean and Mexican cooking.