It is a spice mix of widely varying composition based on South Asian cuisine.
It’s a western, British invention. It is a blend of different powdered spices like turmeric, chili, coriander, cumin, fennel, cinnamon etc. Instead of the various spice powders used in Indian cooking, you can use an already blended curry powder. As inauthentic as curry powder is, I like its convenience.  I needed curry powder for a lamb curry recipe I was making and I didn't have the curry powder, but my cupboard had lots of spices so I went in search of a recipe. I tried this one and it was a hit. Wonderful flavor and color. The wpg_foody, the seeds are green cardamom in the recipe. This is a pretty standard curry powder. What it misses is the best reason to use whole seed -- toasting. As such, I make mine a batch at a time. Adam T. 2013-08-19T14:40:43Z item not reviewed by moderator and published. Curry powder is a spice mix of widely varying composition based on South Asian cuisine. Curry powder and the contemporary English use of the word  curry  are Western inventions and do not reflect any specific South Asian food, though a similar mixture of spices used in north South Asia is called garam masala. Curry powder is actually closer to the Tamil sambar powder, and the word curry is derived from the Tamil word kari meaning sauce, relish for rice. However, use of curry was prevalent in South Asia much before the advent of Europeans in India. Curry powder, a commercially prepared mixture of spices, is largely a Western notion, dating to the 18th century. Such mixtures are commonly thought to have first been prepared by Indian merchants for sale to members of the British Colonial government and army returning to Britain. The main spices found in most curry powders of the Indian subcontinent are turmeric, coriander, and cumin; a wide range of additional spices may be included depending on the geographic region and the foods being included (white/red meat, fish, lentils, rice and vegetables). Makes: 1 cup. British manufacturers developed curry powders in an attempt to provide a ready-made spice mixture equivalent to the kari podi (podi means “powder”) that British colonists became accustomed to in southern India.  Curry powder is a blend of spices which is designed to be used in Indian cooking. In India, cooks prefer to prepare their spices freshly, as needed, ensuring maximum flavor, but it is also possible to purchase packaged curry blends. Cloves are often used in curry powder. Curry powder spice blends typically include ground coriander. Curry powder. Curry powder is often flavored with coriander. Curry powder is a blend of spices commonly Curry powder is a blend of up to 20 different herbs and spices, including the commonly used: cardamom, chiles, cinnamon, cloves, coriander, cumin, fennel, fenugreek, mace, nutmeg, pepper, poppy seeds, sesame seeds, saffron, tamarind and tumeric (which gives curry its characteristic golden color).  Ad. Curry powder also includes many of these spices, blended in a standardized mixture which is intended for use in any sort of dish. Some cooks may start with a base of curry and then add other spices to tweak the taste a little, while others simply use the curry straight. Cloves are often used in curry powder. Curry powder spice blends typically include ground coriander. Curry powder. Curry powder is often flavored with coriander. Curry powder is a blend of spices commonly used in Indian cooking. Curry powder is a generic term for spice mixes used to flavor Indian or Southeast Asian cuisine. Although there is no standard recipe, the main components are usually cumin, coriander, and turmeric. Other common ingredients include: red or black pepper, mustard, ginger, clove, cardamom, bay leaf, and fenugreek. 
http://www.veggiebelly.com/2012/09/taste-test-best-curry-powders.html http://www.foodnetwork.com/recipes/alton-brown/curry-powder-blend-recipe.html#! https://en.wikipedia.org/wiki/Curry_powder https://en.wikipedia.org/wiki/Curry http://www.chowhound.com/recipes/curry-powder-10576 http://www.wisegeek.com/what-is-curry-powder.htm http://www.food.com/about/curry-powder-487 http://www.wisegeek.com/what-is-curry-powder.htm http://foodreference.about.com/od/Ingredients/a/Curry-Powder.htm
what is curry powder