--just means many nerves are affected ("poly" means "many" in Greek word roots).

Most of us here have "polyneuropathy"; it's rare to have neuropathy with only one nerve tract affected ("mononeuropathy") unless the cause is a specific trauma or compressive injury in a particular area. Most systemic causes, be they metabolic (diabetes, thyroid), nutritional, autoimmune, or toxic will effect a large number of nerves.

It's certainly possible, though the "double crush" mechanism I've written about, to have more than one cause compromising nerves; a "mononeuropathy" due to compression, such as an arthritic spinal spur or disc bulge on a spinal nerve root, can be exacerbated by more systemic conditions that would affect many nerve roots. (Spinal radiculopathies are more prevalent in those with diabetes, for example; the compression symptoms at the nerve root are made worse by the nerves already being damaged by blood sugar dysregulation.)