What is the difference between a hematoma and ecchymosis?

A hematoma is a collection of blood outside the blood vessels below the dermal layer of the skin whereas an ecchymosis is collection of blood within the dermal layer. When visible they both appear as a discolouration of the skin with the ecchymosis appearing flat and the hematoma appearing as a swelling. This fact usually distinguishes the two clinically. The colour varies depending on the location and age.