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Gnomes on the Discworld are six inches tall, resembling humans in general body shape, and usually live alone. A gnome has more physical strength than his size would suggest, and sometimes gives painful, bone-cracking hits to people who have underestimated him. The first gnome to appear in the Discworld chronicles made his appearance in a forest area (The Light Fantastic), but in recent years, some gnomes have come to the city of Ankh-Morpork and obtained jobs as tradesmen (Wee Mad Arthur, pest terminator in Feet of Clay) or even Watchmen (Buggy Swires, first appearance as a Watchman in Jingo).

Gnomes are not to be confused with nomes, which are the protagonists in the Bromeliad series. (Except that they're both sub-miniature humanoids living a mainly parasitical existence beneath the notice of the "biggers". So go ahead, be confused.) Gnomes are found on Discworld; Nomes are probably on Roundworld (e.g. the Borrowers.) On the other hand, Gnomes appear to be identical to the Ramtops Nac Mac Feegle, but they may be exiles from the hive-like societies that created them. (Gnomes are found as individual examples; there is no mention of a Gnome society.) Wee Mad Arthur is very like the Feegles; Buggy Swires less so.

A surprising contradiction of the above ideas concerning gnomes is touched upon in The Science of Discworld II: the Globe. Ponder Stibbons and Rincewind are consulting with Hex concerning the difficulties the Faculty are having with a viral infestation of Elves on Roundworld.

A mechanical eyeball about a foot accross lowered itself carefully from the ceiling. Ponder didn't know exactly how it worked, except that it contained vast amounts of incredibly finely drawn tubing. Hex had drawn the plans one night and Ponder had taken them along to the gnome jewellers... (The Science of Discworld II: the Globe, p14)

In other words, gnomes made Hex's scanner-analogue, and work as jewellers in Ankh-Morpork, presumably on the (logical) basis that their tiny hands and fingers would be ideal for incredibly fine metalwork of any kind. This presumes a settled people with mechanical/engineering knoewledge and a certain amount of intellectual curiosity. Yet we've only so far met the other sort of gnome, whose relationship with precious metals and stones would be limited to how much they can carry after robbing the jewellers?