Affixes VII: -on-, -obl-, -op-, -uj-, -um-

-on- cuts a numeral into a fraction. Du gives duono, tri gives triono, kvar gives kvarono, dek gives dekono, cent gives centono. The noun form in -o names the part, duona describes it and duone says how something was done. Whatever the fraction is a fraction of arrives with de, as in duono de la pano.

You already own duono from the core word list, so you have been using the machinery for a while without meeting the suffix.

Its mirror is -obl-, and they differ by three letters in the middle of a word, which is where errors live. Duona is half as much. Duobla is twice as much. Read the whole suffix before you commit to a number.

-obl- multiplies. Du gives duobla, double; tri gives triobla; dek gives dekobla, and the adverb dekoble for tenfold. Stack -ig- on top and you get duobligi, to double something, or with -iĝ-, duobliĝi, to double by itself.

It is the exact mirror of -on-, and the pair is the classic Esperanto slip: duona is half, duobla is twice, and in a hurried sentence about money the difference is a factor of four.

Keep it apart from -op- as well. Triobla is three times as much of something. Triope is three people doing a thing together. One counts the quantity, the other counts the company.

-op- says how many are acting together. The adverb is the usual form: duope, triope, kvarope, unuope. Duopo as a noun names the pair itself, and duopa describes something done in twos.

Two comparisons keep it in place. Against -obl-: triobla is three times as much of something, triope is three people side by side. Against -ar-: an arbaro is a mass of trees nobody has counted, while -op- states the exact size of the group, which is its whole point.

Also keep it away from po, the small preposition for distribution. Po du means two apiece and duope means two at a time, and in speech the pair of them run together far too easily.

-uj- holds three jobs at once, and they are less unlike than they look. It names the container for a mass of the root: mono gives monujo, salo gives salujo. It names the tree that bears the fruit: pomo gives pomujo. And it names the land the people live in: franco gives Francujo, anglo gives Anglujo, germano gives Germanujo. Every result is a noun in -o.

The suffix to keep it apart from is -ing-, which holds exactly one item upright. A kandelingo is a candlestick; a kandelujo would be the box the candles came in.

Country names are the live argument. Francujo, Francio and Franclando are all read without trouble, but -io is what most speakers write today.

-um- is the one affix with no meaning of its own. It marks some relation to the root and leaves you to guess which, so every -um- word has to be learned as vocabulary rather than worked out. Plena gives plenumi, to fulfil; kolo gives kolumo, a collar; mano gives manumo, a cuff; akvo gives akvumi, to water; malvarma gives malvarmumi, to catch a cold. It takes whatever ending the sense needs.

The real rule is that you cannot coin with it and expect to be understood. If a precise suffix exists, use that one instead.

Akvumi is the neat illustration. It means watering the garden. Akvigi, built with the causative, would mean turning something into water, which is not what a gardener is doing at all.