Don't let that last vowel fool you...

Chile powder != Chili powder

Chile powder is simply powdered chilies. Red, spicy chilies such as ancho, chipotle, and cayenne are often used to make the powder and it is commonly used in spicy Mexican dishes such as chili con carne and carne adovada. However, chili powder is a mixture of chile powder and other spices including oregano, cumin, and garlic and onion salt. Chili powder is not as spicy as chile powder and is meant to be used as a flavoring for homemade chili. So be sure to read recipes carefully to verify you are using the proper powder.

lj adds:"in Britain, Chile powder is Chilli powder (And Chilli powder is next-to unheard of, but would probably be called something like 'chilli mix'). I suspect this is due to the much stronger influence of Indian/Pakistani culture compared to that of Mexico/Texas in the UK. I think maybe 'chilli powder' having additional herbs in it may be an America-only thing, but I may well be wrong, and chilli-powder being only made from chillis may be a Britain only thing.

If you would like to make your own chile powder, find some dried chile peppers such as the kinds listed above. Set the peppers in a 350 degree oven for about 10 minutes to ensure they are completely dry. Let the peppers cool completely and then remove the stems and seeds with a sharp knife and cut the peppers into small pieces. Grind the pieces to a fine powder with a spice mill, electric coffee grinder, or a mortar and pestle. The chile powder should be kept in a dry dark pantry and should keep its flavor for several months.