Peripheral neuropathy refers to damage or dysfunction of the peripheral nervous system, which can involve single nerves (mononeuropathy), multiple individual nerves (mononeuropathy multiplex), or nerve plexuses (plexopathy). Mononeuropathy affects a single nerve and can result from pressure or injury. Mononeuropathy multiplex involves multiple individual nerves in a random pattern, often due to vascular or connective tissue diseases. Plexopathy involves damage to nerve plexuses, commonly the brachial plexus, which can be caused by trauma, tumors, or other medical conditions.