noun, plural: haematomas or haematomata or haematomae
Haematoma is a localized collection of blood outside the blood vessel in an organ, space, or tissue. It is usually clotted. It results from a break in the wall of a blood vessel. Possible causes of blood vessel wall breakage leading to haematoma include trauma, disease, injury, and surgery. It begins in liquid form and then spreads among the tissues. It may then coagulate and solidify prior to reabsorption into the blood vessels.
Haematoma may be classified according to the degree affected. When only a small pinpoint of the skin (i.e. less than 3 mm in diameter), for instance, is affected, it is referred to as petechiae. When the haematoma is about 1 cm in diameter and generally round in shape it is referred to as purpura (bruise). When a hematoma of the skin is over 1 cm in diameter it is referred to as ecchymosis.
Word origin: Ancient Greek haímatos, haîma (blood), and Ancient Greek -ōma (denoting disease)