Esperanto Etymology - Inflections

Inflections

The Greek origin of the nominal inflections can be seen in the Greek a-declension nouns such as the word for "muse": musa, plural musai, accusative musan, which in Esperanto is muzo, muzoj, muzon. Greek o-declension words such as logos, logoi, logon (word) are similar, as are adjectival declensions such as aksia, aksiai, aksian (worthy). Greek was perhaps also the model of stressed i in Esperanto words like familío (family), which follows the common Greek pattern of aksía (worthy) and ojkíaj (houses).

Esperanto also has an a–i–o ablaut for present/past/future tense, which has partial parallels in Latin present amat, perfect amavit, and the corresponding infinitives amare, amavisse. Otto Jespersen said of the ablaut,

This play of vowels is not an original idea of Zamenhof's: -as, -is, -os are found for the three tenses of the infinitive in Faiguet's system of 1765; -a, -i, -o without a consonant are used like Z's -as, -is, -os by Rudelle (1858); Courtonne in 1885 had -am, -im, -om in the same values, and the similarity with Esperanto is here even more perfect than in the other projects, as -um corresponds to Z's -us. —An International Language (1928)

There may also have been a Volapük influence: there the vowels were present a-, future o-, past perfect i-, as well as imperfect ä- ; Esperanto retained a distinction between preterite -is and an imperfect in -es until 1887, the year the modern form of the language was published.

The infinitive suffix -i may derive from Latin deponent verbs, such as loqui (to speak). With elements like these that are only one or two letters long, it is difficult to know whether resemblances are due to the forms being related, or just coincidence. For example, it is speculated that the jussive -u is from the Hebrew imperative -û, but it could also be from the Greek imperative of deponent verbs such as dekhou (receive!); or perhaps it was inspired by being found in both Hebrew and Greek. Similarly, adverbial -e is found in Latin and Italian (bene) as well as in Russian (after a palatalized consonant); the participle bases -t- and -nt- are found in Latin, Italian, Greek, and German; and the pronominal base -i is found in Italian (-mi, -ti, -vi, -si, -gli for Esperanto mi, ci, vi, si, li) and English (me, we, he, she).