In meicine, an embolism occurs when an object (the embolus, plural emboli) migrates from one part of the body (through circulation) and causes a blockage (occlusion) of a blood vessel in another part of the body. The term was coined in 1848 by Rudolph Carl Virchow. Contrast this with a thrombus, or clot, which forms at the blockage point within a blood vessel and is not carried from somewhere else.