Word-building can be made quite an amusing game for children. For instance, give them the suffixes -ej (denoting place) and -il (denoting instrument), and set them to form words for "school," "church," "factory," "knife," "warming-pan," etc. (lernejo, preĝejo, fabrikejo, tranĉito, varmigilo).
But since the language is perfectly regular in form and construction, and the learner can therefore argue from case to case, it is a useful instrument for instilling clear ideas of grammatical categories. Thus give the roots—
| viv‑i = to live | san‑a = healthy | hom‑o = man | ||
| long‑a = long | saĝ-a = wise | Di‑o = God | ||
| don‑i = to give |
and set such sentences as the following to be worked out—
"He lives long"; "A long life is a gift of God"; "It is wise to live healthily"; "God is divine, man is human"; "Human life is short," etc.
The same roots constantly recur with an -o, -a, or -e tacked on; and the practice in sorting out the endings, and attaching them like labels to nouns, adjectives, verbs, and adverbs, soon marks off the corresponding ideas clearly in the learner's mind.
Analogous to simple sums and conducive to clear thinking are such sentences as the following, for rather more advanced pupils:
Given—
| raz‑i = to shave | serv‑i = to serve | san‑a = healthy | ||
| akr‑a = sharp | mort‑i = to die | ven‑i = to come | ||
| uz‑i = to use | hak‑i = to hew | kun = with | ||
| sent‑i = to feel |
and the [table of affixes].