Complex sentence: A subungual hematoma is a collection of blood (hematoma) underneath a toenail or fingernail which often results from a traumatic injury such as slamming a finger in a door.
Split into simpler sentences: A subungual hematoma is a collection of blood (hematoma) underneath a toenail or fingernail. It often results from a traumatic injury such as slamming a finger in a door.