Ido inherits many of the same grammatical features of Esperanto, and in many cases the vocabulary is similar. Ido shares with Esperanto the goals of grammatical simplicity and consistency, ease of learning, and the use of loan words from various European languages. However, certain changes were introduced to address some of the concerns that had arisen about Esperanto. These include:
- Esperanto's alphabet uses six new letters, three of which which are not found in any existing language; as a result, Esperanto in typing and in internet e-mail and newsgroups frequently resorts to any of several schemes to represent these special letters. This leads to the situation where the same word may be displayed any of several different ways. Ido addresses this issue by using the 26-letter English alphabet.
- For reasons of grammatical simplicity, Esperanto generally does not impose rules of grammatical agreement between grammatical categories within a sentence, since these are redundant. For example, in Esperanto, the verb in a sentence is invariable regardless of the number and person of the subject. But this principle was not extended in Esperanto to adjectives and nouns; as a result, in Esperanto, an adjective must agree in number and case with the noun it modifies. There is no such requirement in English, for example, where number is emphasized by variation of the verb, and Ido eliminates this feature from its grammar.
- Esperanto requires the use of the -n ending to signify the use of the accusative case. Ido allows the use of this feature in ambiguous situations where the object of a sentence does not follow the subject, but in all other situations the accusative case was eliminated as redundant.
- Ido imposes consistent rules on the use of endings to tranform a word from one meaning or part of speech to another, thus simplifying the amount of vocabulary memorization that is necessary.
- Ido, unlike Esperanto, does not assume the male gender as the default, and thus does not, for example, define a sister as a female-brother, as Esperanto does.
- The Ido vocabulary attempts to share cognates with as many of the major Western European languages as possible, while Esperanto includes roots from other sources.
Each word in the Ido vocabulary is built from a root word. A root word consists of a root and a grammatical ending. Other words can be formed from that word by removing the grammatical ending and adding a new one, or by inserting certain affixes between the root and the grammatical ending. Ido is grammatically invariable; there are no exceptions in Ido, unlike in natural languages.
Some of the grammatical endings are defined as follows:
- -o : noun
- -a : adjective
- -e : adverb
- -ar : verb infinitive
- -as : verb, present tense
- -is : verb, past tense
- -os : verb, future tense
much more about Ido grammar can be explained here, such as pronouns, affixes, references to the history of the language
When the request by the Delegation for the Adoption of an International Auxiliary Language to the International Association of Academies in Vienna to select an international language was rejected in May, 1907, the Delegation accepted a slate of candidates proposed by Louis Couturat, the founder of the Delegation, to meet as a Committee in Paris in October 1907 to discuss the adoption of a standard international language among the various competitors that had been devised up to that time. According to the minutes of the Committee, it decided that no language was completely acceptable, but that Esperanto could be accepted "because of its relative perfection and because of the many and divers applications already received by it, on condition of several modifications to be realized by the permanent Commission in the direction defined by the conclusions of the Report of the Secretaries (Couturat and Leopold Leau) and by the Ido project" which latter had been presented to the Committee as an anonymous project, which has later been suggested to have been primarily devised by Couturat with some help from Esperanto's representative before the Committee, Louis de Beaufront. (Beaufront had himself argued for reforming Esperanto prior to having been selected to the Delegation, and during the proceedings he argued in favor of Esperanto over other languages; his "conversion" to the Ido camp upon the presentation of that language was thus consistent with earlier positions, given his previous arguments for making changes to Esperanto.)
The inventor of Esperanto, L. L. Zamenhof, as well as many of the language's supporters, resisted any effort at improving it, even though several of the reforms adopted by Ido were themselves proposed at various times by Zamenhof. This resistance to addressing potential faults in Esperanto has continued to the present day. Couturat, who was the leading proponent of Ido, was killed in an automobile accident in 1914, which, along with World War I which began at much the same time, dealt a serious blow to the Ido movement. Although that movement recovered to some degree in the immediate postwar period, his death was essentially a fatal blow, and the whole movement of international languages became Balkanized as a result. The publication of an even more Europeanized planned language, Occidental, in 1922 began the process of splintering the community, and the Ido movement lost a majority of its published periodicals in the subsequent year or so, and the defection of its major intellectual supporter, the Danish linguist Otto Jespersen, in 1928 on the occasion of the publication of his own planned language Novial, seemed at the time to provide a quietus. However, the language still has a few speakers today, and the internet has sparked a renewal of interest in the language in recent years.
Jespersen, who was present during the ten days of Committee deliberations in Paris and later served as part of the permanent Commission, wrote a history of Ido.
Many Esperanto supporters have attacked Ido over the years. One of them, Don Harlow, wrote a history of Ido in The Esperanto Book, in his third chapter, "How to Build a Language". There have been many questions about the validity of his history, to which he replies in a subchapter, "Ido: The Beginning". However, a few Ido partisans argue that Harlow's history does not jibe with all the eyewitness accounts, such as those reported by Jespersen, although it is based on material from some other other eyewitnesses such as Emile Boirac and Gaston Moch and with some source documentation, to which Jespersen did not have access (such as Zamenhof's correspondence with Couturat and others during the period).
- Page about the Ido language
- Otto Jespersen's history of Ido
- Another history of Ido
- Don Harlow's "How to Build a Language", the section about Ido
- Don Harlow's "Ido: The Beginning"
- Emile Boirac's "Report to the World Esperanto Congress, 1908" about his experiences as part of the Delegation's Committee