It has already been remarked that the bare stem-form of many adjectives would not be euphonious enough, and that it is therefore often convenient to have a vowel added to it: i is the best for that purpose, and we therefore have such N adjectives as simpli, nigri black, posibli, stranji, singli, propri own, etc. Even where the adjective ends in only one consonant, the same -i may optionally be appended to it for euphony, especially before words beginning with consonant groups; thus we have alternative forms like bon boni good, kruel krueli, matur maturi, sam sami, publik publiki, etc.
The choice of i for this purpose is justified (besides by the fact that a, e, o are otherwise occupied) by many derivatives like simpli-fika = fika simpli (below, p. 137), modernisa.
In some adjectives -i corresponds to E -ic (-ical): elektri, identi, kosmopoliti, fanati, etc.
When adjectives are made into primaries, we have the endings already considered, for persons -e, -o, -a, and for neuter -um. If the adjective is used by itself with reference to a substantive just mentioned ("anaphorically") the ending -i is retained, and a plural may be formed in -is: hir es du roses, li blanki es plu bel kam li redi the white one ... the red one. Hir es multi roses: ob vu prefera li blankis o li redis? Inter lon libres es multis in anglum e kelkis in latinum, ma lo lekte nur li anglis. Similarly: li maxim oldis ek lon libres the oldest ones among his books.
The definite article is a secondary and therefore uninflected in number or gender; its proper form should be the single sound l, but this is impracticable except in close connexion with some of the prepositions: al, del, dal (prol, pril are not so good); in all other cases we add -i, so that the usual form of the article is li (= Occ).