Ido (pronounced /idɔ/) is a constructed language created with the goal of becoming a universal second language for speakers of different linguistic backgrounds as a language easier to learn than ethnic languages. This intended usage parallels the current use of English as a lingua franca, and of French, Latin, and Greek in earlier eras. Unlike English, which is a natural and frequently irregular language, Ido was specifically designed for grammatical, orthographic, and lexicographical regularity, and to favor no one who might otherwise be advantaged in a situation due to native fluency in a widespread language. In this sense, Ido is classified as a consciously created International Auxiliary Language (conIAL). Of the most widely used conIALs, the first one is Esperanto, Ido's predecessor; it is disputable whether the second place in usage goes to Ido or Interlingua.
Ido was developed in the early 1900s, and retains a sizable following today, primarily in Europe. It is largely based on Esperanto, created by L. L. Zamenhof. Ido first appeared in 1907 as a result of a desire to reform perceived flaws in Esperanto that some of its supporters believed to be a hindrance in its propagation as an easy-to-learn second language. Many other reform projects appeared after Ido: examples such as Occidental and Novial appeared afterwards but have since faded into obscurity. At present, Ido along with Esperanto and Interlingua are the only auxiliary languages with a large body of literature and a relatively large speaker base. The name of the language likely traces its origin to the Ido pronunciation of "I.D." (from "International Delegation", see below) or the word esperantido, "descendant (of Esperanto)". Or, as with the case of "Esperanto", it could simply be adopted from the pseudonym its designer (Louis Couturat) used in presenting the language to the Delegation Committee. In IDO, it is simply an abbreviation of Idiomo Di Omni (language for all).
Ido uses the 26 Latin letters used in the English alphabet with no diacritics. While still being completely morphologically regular, Ido resembles the Romance languages in appearance and is sometimes mistaken for Italian or Spanish at first glance. Ido is largely intelligible to those who have studied Esperanto, though there are certain differences in word formation, grammar and grammatical-function words that make it more than a simple reform project. Ido is a stand-alone language.
After its inception, Ido gained support (estimates generally range around 20%) from some in the Esperanto community at the time, but following the sudden death in 1914 of one of its most influential proponents, Louis Couturat, it declined in popularity. There were two reasons for this: first, the emergence of further schisms arising from competing reform projects; and second, a general lack of awareness of Ido as a candidate for an international language. These obstacles weakened the movement and it was not until the rise of the Internet that it began to regain its former momentum.

History

Main article: Esperanto and Ido compared Comparison with Esperanto
Ido has the same typical five-vowel system (a, e, i, o, u have their IPA values) as Esperanto, and most of the same consonants, omitting two consonant phonemes used by Esperanto, IPA /x/ and /ʤ/. (The distinctions between /x/ : /h/ and between /ʤ/ : /ʒ/ carry a very low functional load in Esperanto, and so were deemed to be unnecessary in Ido.) Without those two consonant phonemes, the consonants in the language are as follows:
The accent rule in Ido is regular, but slightly more complex than that of Esperanto: all polysyllables are stressed on the penultimate (second from last) syllable except for verb infinitives, which are stressed on the ultimate syllable—skolo, kafeo and lernas for "school", "coffee" and "learn", but irar, savar and drinkar for "to go", "to know" and "to drink". If an i or u precedes another vowel, the pair is considered part of the same syllable when applying the accent rule—thus radio, familio and manuo for "radio", "family" and "hand".

Phonology
Each word in the Ido vocabulary is built from a root word. A 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. As with Esperanto, Ido is grammatically invariable; there are no exceptions in Ido, unlike in natural languages.
Some of the grammatical endings are defined as follows:
These are the same as in Esperanto except for -i, -ir, -ar, -or and -ez. Esperanto marks noun plurals by an agglutinative ending -j (so plural nouns end in -oj), uses -i for verb infinitives (Esperanto infinitives are tenseless), and uses -u for the imperative. Verbs in Ido do not conjugate depending on person, number or gender; the -as, -is, and -os endings suffice whether the subject is I, you, he, she, they, or anything else.

Grammar
Ido word order is generally the same as English (subject verb object), so the sentence Me havas la blua libro is the same as the English "I have the blue book", both in meaning and word order. There are a few differences, however:
Negation occurs in Ido by simply affixing ne to the front of a verb: Me ne havas libro means, "I do not have a book". This as well does not vary, and thus the "I do not", "He does not", "They do not" before a verb are simply Me ne, Il ne, and Li ne. In the same way, past tense and future tense negatives are formed by ne in front of the conjugated verb. "I will not go" and "I did not go" become Me ne iros and Me ne iris respectively.
Yes/no questions are formed by the particle ka in front of the question. "I have a book" (me havas libro) becomes Ka me havas libro? (do I have a book?). Ka can also be placed in front of a noun without a verb to make a simple question, corresponding to the English "is it?" Ka Mark? can mean, "Are you Mark?", "Is it Mark?", "Do you mean Mark?" depending on the context.

Adjectives can be written either before the noun as in English, or after the noun as in French. Thus, Me havas la libro blua is also permissible.
Ido has the optional -n accusative ending that is used when the object of the sentence is not clear, or it may be used to alter word order when desired. La blua libron me havas is another acceptable way of saying the same thing. Syntax
The pronouns of Ido were revised to make them more acoustically distinct than those of Esperanto, which all end in i. Especially the singular and plural first-person pronouns mi and ni may be difficult to distinguish in a noisy environment, so Ido has me and ni instead. Ido also distinguishes between intimate (tu) and formal (vu) second-person singular pronouns as well as plural second-person pronouns (vi) not marked for intimacy. Furthermore, Ido has a pan-gender third-person pronoun lu (it can mean "he", "she", or "it", depending on the context) in addition to its masculine (il), feminine (el), and neuter (ol) third-person pronouns.
¹ ci, while technically the familiar form of the word "you" in Esperanto, is almost never used. Results on Google have shown that while tu is only slightly less common than vu in Ido, ci is used less than half of one percent of the amount vi is in Esperanto. Esperanto's inventor himself did not include the pronoun in the first book on Esperanto and only later reluctantly; later he recommended against using ci on the grounds that different cultures have conflicting traditions regarding the use of the familiar and formal forms of "you", and that a universal language should avoid the problem by simply using the formal form in all situations. Unlike some other languages that use a formal second person pronoun, vi is not capitalized.
² tiu, though not a pronoun, is usually used in this circumstance, because many people have a hard time applying "it" to humans.
It should be noted that ol, like English it and Esperanto ĝi, is not limited to inanimate objects, but can be used "for entities whose sex is indeterminate: babies, children, humans, youths, elders, people, individuals, horses, cows, cats, etc."
Lu is often mistakenly labeled an epicene pronoun, that is, one that refers to both masculine and feminine beings, but in fact, lu is more properly a "pan-gender" pronoun, as it is also used for referring to inanimate objects. From Kompleta Gramatiko Detaloza di la Linguo Internaciona Ido by Beaufront:
Lu (like li) is used for all three genders. That lu does duty for the three genders at will in the singular is not in itself any more astonishing than seeing li serve the three genders at will in the plural ... By a decision (1558) the Idist Academy rejected every restriction concerning the use of lu. One may thus use that pronoun in exactly the same way for a thing and a person of obvious sex as for animals of unknown sex and a person that has a genderless name, like baby, child, human, etc., these being as truly masculine as feminine.
The motives for this decision were given in "Mondo", XI, 68: Lu for the singular is exactly the same as li for the plural. Logic, symmetry and ease demand this. Consequently, just as li may be used for people, animals, and things whenever nothing obliges one to express the gender, so lu may be used for people, animals, and things under the same condition. The proposed distinction would be a bothersome subtlety...

Pronouns
Vocabulary in Ido is based on words intended to give the greatest facility to the most speakers. Early on, the first 5000+ roots were analyzed compared to the vocabulary of English, French, Spanish, German, Russian and Italian, and the following result was found: Adoption of a word is done through consensus, after which the word will be made official by the union. Care must also be taken to avoid homonyms if possible, and usually a new word undergoes some discussion before being adopted. Foreign words that have a restricted sense and are not likely to be used in everyday life (such as the word intifada to refer to the conflict between Israel and Palestine) are left untouched, and often written in italics.

2024 roots (38%) belong to 6 languages
942 roots (17%) belong to 5 languages
1111 roots (21%) belong to 4 languages
585 roots (11%) belong to 3 languages
454 roots (8%) belong to 2 languages
255 roots (5%) belong to 1 language

• Total 5371 100%
  French 4880: 91%
  Italian 4454: 83%
  Spanish 4237: 79%
  English 4219: 79%
  German 3302: 61%
  Russian 2821: 52%
  The diminutive suffix -et-. Domo (house) becomes dometo (cottage), and libro (book) becomes libreto (novelette or short story).
  The pejorative suffix -ach-. Domo becomes domacho (hovel), and libro becomes libracho (a shoddy piece of work, pulp fiction, etc.)
  The prefix retro-, which implies a reversal. Irar (to go) becomes retroirar (to go back, backward) and venar (to come) becomes retrovenar (to return). Vocabulary
  As with all constructed languages, gauging the number of speakers of Ido is an extremely difficult task. Usenet postings by the prominent Esperantist Don Harlow have estimated the population at being somewhere in the thousands, but no accurate numbers exist. Moreover, given the often political IAL environment in which those that speak a language are not merely language users but adherents to its system and linguistic philosophy as well, there are two categories of those that know the language, Ido speakers and Ido supporters. Ido resembles Esperanto to a large extent, and many Esperantists have learned Ido out of curiosity while still not using it, preferring to support the more well-known Esperanto movement instead. On one Esperanto bulletin board was written the following:
  Mi provis Idon antaŭ Esperanto, kaj alvenis konklude: la diferoj estas efike trivialaj, komparite al pli gravaj koncernaĵoj (kiujn mi ne detalos ĉi tie). Pro tio mi elektis subteni Esperanton, kaj ne subteni Idon, kvankam eble mi lernos Idon por hobio. Tamen via id-vortoj estas bone komprenebla al mi, kaj mi uzus Idon, se ne ekzistis tre pli subtenita lingvo.
  I tried Ido before Esperanto, and came to conclude that the differences are in fact trivial, compared to larger concerns (that I will not go into detail about here). For that [the larger speaker community and volume of material] I chose to support Esperanto and not to support Ido, though maybe I will learn Ido as a hobby. However, your writing in Ido [responding to an Ido speaker] is comprehensible to me, and I would use Ido if there did not exist a much more supported language.
  It is possible to find discussions of this nature on the Internet in English, Esperanto, Ido, Interlingua and other IALs, each understanding the other with little problem.
  A small sample of 24 Idists on the Yahoo! group Idolisto during late 2005 showed that 57% had begun their studies of the language during the past three years, 32% from the mid-1990s to 2002, and 8% had known the language from before.
  
  Ido-speaking community
  
  La Princeto (The Little Prince)
  Translation of tune by Russian bard Alexandr Sukhanov from verses by Russian poet Yunna Morits. (listen)
  Me nule savas la Angla, la Franca, la Greka,
  Mea vid-cirklo do restas sat mikra e streta -
  En mea vid-cirklo trovesas nur flori, arbori,
  Nur tero e maro, aero, fairo, amoro.
  Me nule savas la Dana e la Portugala,
  Mea vid-cirklo restas sat infantala -
  Nur joyi rapide pasant', bruligiva aflikto,
  Nur esperi, e timi noktal' es en mea vid-cirklo.
  Me savas nek la Sanskrito e nek la Latina,
  Mea vid-cirklo es ancien-mod' quale tino
  Nur morto e nasko homala, nur grani ed astri
  Aden mea vid-cirklo penetras e standas sat mastre.
  Mea savo artala esas fakultativa.
  Mea vid-cirklo restas presk' primitiva -
  En olu es nia afero intima, interna
  Por ke kun homaro la Tero flugadez eterne.
  Mea vid-cirklon restriktas nur timi, esperi,
  En olu trovesas nur amo, nur maro e tero.
  Aden mea vid-cirklo penetras e standas sat mastre
  Nur morto e nasko homala, nur grani ed astri.
  
  Mea vido-cirklo (horizonto)
  Ido has a number of publications that can be subscribed to or downloaded for free in most cases. Kuriero Internaciona is a magazine produced in France every few months with a range of topics. Adavane! is a magazine produced by the Spanish Ido Society every two months that has a range of topics, as well as a few dozen pages of work translated from other languages. Progreso is the official organ of the Ido movement and has been around since the inception of the movement in 1908. Other sites can be found with various stories, fables or proverbs along with a few books of the Bible translated into Ido on a smaller scale. The site publikaji has a few podcasts in Ido along with various songs and other recorded material.
  The online encyclopedia Wikipedia includes an Ido-language edition (known in Ido as Wikipedio); as of December, it has over 14,000 articles.
  
  Literature and publications
  
  2007: Paris, France (Information)
  2006: Berlin, Germany, approx. 25 participants from 10 countries (Raporto)
  2005: Toulouse, France, 13 participants from 4 countries (Raporto)
  2004: Kiev, Ukraine, 17 participants from 9 countries (Raporto)
  2003: Grossbothen, Germany, Participants from 6 countries (Raporto)
  2002: Kraków, Poland, 14 participants from 6 countries (Raporto)
  2001: Nürnberg, Germany, 14 participants from 5 countries (Raporto)
  1998: Białobrzegi, Poland, 15 participants from 6 countries
  1997: Bakkum (mun. Castricum), Netherlands, 19 participants from 7 countries
  1995: Elsnigk, Germany
  1991: Ostend, Belgium, 21 participants
  1980: Namur, Belgium, 35 participants
  1960: Zürich, Switzerland, ca. 50 participants Overview and answers to common questions
  
  Langmaker.com about Ido
  Otto Jespersen's history of Ido
  Another history of Ido
  Emile Boirac's "Report to the World Esperanto Congress, 1908" about his experiences as part of the Delegation's Committee
  Léopold Leau's "The Truth About the Delegation in 1907", a rebuttal of criticisms made about the events of the Delegation, based on his own experiences as a member of the Delegation
  "How to Build a Language", the section about Ido, and "Ido: The Beginning" by Don Harlow
  Ido-Pagino da Ailanto - Discussion about Ido, links to websites, organizations, mailing lists, courses, dictionaries, grammars, etc.
  Blueprints for Babel: Ido - Commentary and grammatical summary of Ido, with glossary and links