Esperanto words with the infix -um-

Such derivations must be memorized individually, though because the root already exists, they may be more easily learned than a completely new word.

One area where the derivations is -um- are nearly predictable is in pieces of clothing named after the corresponding parts of the body:[1][2] kolumo 'collar' (from 'neck'); buŝumo 'muzzle' (from 'mouth'); manumo 'cuff' (from 'hand': does not mean 'glove'); kalkanumo 'heel (of a shoe)'; plandumo 'sole (of a shoe)'; ingvenumo 'jockstrap' (from 'groin'); hufumo 'horseshoe' (from 'hoof'); nazumo 'pince-nez, spectacles' (from 'nose', now uncommon).

In a similar vein, cicumo is a 'nipple (on a bottle)', from '(human) nipple' (body-part extension), and fenestrumo is 'shutter', from 'window' (a covering of a part).

Forms of execution also take -um-: krucumi 'to crucify', pendumi 'to hang', gasumi 'to gas', ŝtonumi 'to stone', dekumi, kvaronumi 'to quarter', palisumi 'to impale', radumi 'to break on the wheel'.

Similarly, amikumi means 'to pass time with one's friends'; esperantumi 'to spend time using Esperanto'; kafumi 'to have a cup of coffee', retumi 'to surf the Web' (from reto 'net, Internet'), and urbumi 'to go into town' (from urbo 'town, city').