- related in an unspecific way. A lexical suffix with no fixed meaning or part of speech.
- brako (“arm”) + -um- → brakumi (“to hug”)
- dekstra (“right”) + -um- → dekstruma (“clockwise”)
- komuna (“common”) + -um- → komunumo (“community”)
- mondo (“world”) + -um- → mondumo (“high society”)
- proksima (“near”) + -um- → proksimume (“approximately”)
- kruco (“cross”) + -um- → krucumi (“to crucify”)
- kolo (“neck”) + -um- → kolumo (“collar”)
Because meanings of words derived with this suffix cannot be predicted, each derivation requires a separate dictionary entry. The part of speech is specific to each coining, and not inherent in either the suffix or the stem to which it is attached.
Among other uses:
- With body parts, -um- may signify a related piece of clothing: kolumo, manumo, plandumo, nazumo, hufumo. Or it may signify an action using that body part: brakumi, palpebrumi, okulumi.
- With things used to kill people, -um- may signify a method of execution: gasumi, ŝtonumi, krucumi.
- With numbers, -um- may signify a numeric base: duuma, okuma, dekuma.
- With things enjoyed at leisure, -um- may signify a leisure activity: butikumi, fumumi, bierumi, esperantumi.
- an agent trigger infix
- suffix to be used only in specific cases where the meaning is also specified
The suffix -um- has an indeterminate meaning. The derivations of this suffix is only made by the Language Committee of Ido. It forms derivation, of which the meaning has a indefinite relation with the idea expressed by the prime root. The link which remain between them helps with the memorization, but, when one doesn't know the meaning of the derivation, only the lexicon can surely provide it. There exists only a total of 30 words with this suffix in Ido.
- Infix form of um-.