Grizzly bears have a shoulder hump. American Black bears have flat shoulders.
Grizzly bears - Concave Black bears - Straight
Grizzly bears are found only in Canada and 5 states of the US - Alaska, Montana, Wyoming, Washington, and Idaho. Black bears have a larger range both in the US and Canada.
Typically, Grizzly bears have brown fur and black bears have black fur but, the color can vary. Some Grizzly bears can have blackish fur. Some black bears can have brown fur.
The Grizzly bear is a SUBSPECIES of brown bear. Scientific name - Ursus arctos horribilis The American Black bear is a bear SPECIES with many subspecies. Scientific name - Ursus americanus