Proto-Esperanto is the modern term for any of the stages in the evolution of L. L. Zamenhof's language project, prior to the publication of Unua Libro in 1887.
The ''Lingwe uniwersala'' of 1878
As a child, Zamenhof had the idea to introduce an international auxiliary language for communication between different nationalities. He originally wanted to revive some form of simplified Latin or Greek, but as he grew older he came to believe that it would be better to create a new language for his purpose. During his teenage years he worked on a language project until he thought it was ready for public demonstration. On December 17, 1878, Zamenhof celebrated his 19th birthday and the birth of the language with some friends, who liked the project. Zamenhof himself called his language Lingwe Uniwersala. W is used for v. Otherwise, all modernEsperanto letters are attested apart from ĉ, ĝ, ĥ, ĵ, ŝ, ŭ. Known verb forms are present -á, imperative -ó, infinitive -are. Nouns were marked by -e in the singular and -es in the plural; the article was singular la and plural las. It appears that there was no accusative case, and that stress was as in modern Esperanto, except when marked, as in -á and -ó. Only four lines of the Lingwe uniwersala stage of the language from 1878 remain, from an early song that Zamenhof composed: In modern Esperanto, this would be, Jam temp' está remains an idiom in modern Esperanto, an allusion to this song.
The ''Lingvo universala'' of 1881
While at university, Zamenhof handed his work over to his father, Mordechai, for safe-keeping until he had completed his medical studies. His father, not understanding the ideas of his son and perhaps anticipating problems from the Tsarist police, burned the work. Zamenhof did not discover this until he returned from university in 1881, at which point he restarted his project. A sample from this second phase of the language is this extract of a letter from 1881: Modern: Mia plej kara amiko, neniam mia senkulpa plumo fariĝus tirano por vi. Mi povas de cent viaj leteroj konkludi, kiel sciigoj de tiu-ĉi speco devas vundi vian fratan koron; mi kvazaŭ vidas vin jam... By this time the letter v had replaced w for the sound; verbal inflection for person and number had been dropped; the nominal plural was -oj in place of -es ; and the noun cases were down to the current two. The accusative case suffix was -l, but in many cases was only used on pronouns: Beside the stronger Slavic flavor of the orthography compared to the modern language, the imperfective verb forms still had final stress: The pronouns ended in a nominal o, but there were other differences as well, including a conflation of 'he' and 'it': In addition, there was indefinite o 'one'. The correlatives were similarly close, though it is not clear if there was a distinction between indefinite and relative forms and no possessive forms are known: The last row was evidently pronounced as fj-. Esperanto at this stage had a consonantal ablaut in verbs, with a voiceless consonant for an attempt at something, and a voiced consonant for success. For example, aŭti to listen, aŭdi to hear; trofi to look for, trovi to find; prufi to argue, pruvi to prove. Traces of this remain in a few pairs of words such as pesi 'to weigh ' and pezi 'to weigh '.
Transition to the modern Esperanto of 1887
Zamenhof refined his ideas for the language for the next several years. Most of his refinements came through translation of literature and poetry in other languages. The final stress in the verb conjugations was rejected in favour of always stressing the second-last vowel, and the old plural -s on nouns became a marker of finite tenses on verbs, with an imperfect -es remaining until just before publication. The Slavic-style acute diacritics became circumflexes to avoid overt appearances of nationalism, and the new bases of the letters ĵ, ĝ helped preserve the appearance of Romance and Germanic vocabulary. In 1887 Zamenhof finalized his tinkering with the publication of the Unua Libro'', which contained the Esperanto language as we know it today. In a letter to Nikolai Borovko he later wrote,
Later proposals by Zamenhof
By 1894, several proposals of changes on Esperanto had appeared. Zamenhof was pressured to answer and presented a reformed version himself. The changes were not well received by the community and were later rejected by Zamenhof.
