As per wikipedia these are the definitions:
A contusion, commonly known as a bruise, is a type of hematoma of tissue in which capillaries and sometimes venules are damaged by trauma, allowing blood to seep, hemorrhage, or extravasate into the surrounding interstitial tissues. 1
A hematoma (US spelling) or haematoma (UK spelling) is a localized collection of blood outside the blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillaries. 2
Bleeding, also known as hemorrhaging or haemorrhaging, is blood escaping from the circulatory system.3
So, is contusion a hematoma due to trauma? Is haemorrhage a technical term for bleeding (even simple ones)?