To find a proper substitute for coriander, you first need to understand what your recipe means by "coriander". In the United States, "coriander" typically refers to coriander seed or ground coriander, while "cilantro" is the term used to refer to the fresh leaves of the coriander plant. In the UK, however,"coriander" refers to the fresh leaves, and the seeds are referred to as "coriander seed" or "ground coriander". Confusing? Definitely. But once you understand what your recipe is asking for, finding a substitute is a snap:
Cilantro/Coriander Leaf Substitute
Replace the coriander called for in the recipe with an equal amount of fresh parsley, tarragon, dill or a combination of the three.
Coriander Seed/Ground Coriander Substitute
Replace the coriander called for in the recipe with an equal amount of carraway seeds, cumin, fennel or a combination of the three.