Curry Leaf
Curry leaves are the leaves of the curry tree. The curry tree is native to India and Sri Lanka.
The leaves are often used fresh and whole in Indian curry dishes.
Curry Powder
Does the term <i>Curry Powder</i> refer to ground dried curry leaves? No. Actual curry leaves are hard to find, and when packaged they are labeled as curry leaves or curry leaf powder.
The term <i>Curry Powder</i> refers to a commercial mix of spices. The mix varies. It may include ginger, garlic, pepper, chilli, and other spices, and it may or may not include some curry leaves.
According to this [https://www.youtube.com/watch?v=LaEHhnIKVeI youtube], a style of curry powder was introduced to UK in seventeenth century along the lines of the popular 'kitchen pepper' used in recipes since 1682 with ginger, pepper, cloves, nutmegs and cinnamon.
Curry
The term <i>Curry</i> is now used worldwide to refer to any savory stew served over rice.
Its origins may have something to do with the curry tree and its leaves. And it may come from the Tamil word kari which means a relish sauce for rice.