--referring to nerve problems outside the brain and spinal cord, but there's often a need to be more specific.

SFN = small fiber neuropathy: problems with the small, unmyelinated nerves that subsume the sensations of pain and temperature, and also underlie most autonomic functioning.

LFN = large fiber neuropathy: problems with the larger, myelinated nerves that subsume sensations of vibration, postion, and mechanical touch. Also all motor function--motor nerves are myelinated.

Polyneuropathy just refers to many nerves being involved, as opposed to mononeuropathy, which is disruption along one nerve pathway. Sometimes, you'll see reference to mutliple mononeuropathies; that's when the situation isn't global throughout the body, but involves several individual nerve pathways. This can happen with compression of nerve roots from the spinal cord, for example--if one has pressure on several nerve roots, this is a mutliple mononeuropathy. Nerve root problems are also called radiculopathy--literally, problem with the root (radic is Latin for root).

After that, one can get into a bewildering group of specific syndromes, such as CIDP--chronic inflammatory demyelinating polyneuropathy. At least that term is descriptive--they aren't always.