Table of Contents
  1. Author's Note
  2. History of Ido
  3. Nouns
  4. Verbs
  5. Adjectives and Adverbs
  6. Pronouns
  7. Derivations
  8. Questions
  9. Affixes

Author's Note

I apologize in advance for the frequent comparisons to Japanese and German. As these are the only languages I have had training in, they are the only ones at my disposal. If you would like to contribute comparisons, it would be much appreciated.

This is not intended to be an authoritative text on the Ido language but rather a lengthy introduction. As I learn more of the language and its rules, I will expand this writeup; perhaps some day, it will serve as a complete manual, but that day is not today. If you are interested in formal specifications and dictionaries for Ido, I have included the address of the International Language (Ido) Society of Great Britain, which seems to be the international body for Ido. They sell many books on the subject.

Also, I use Unicode in this writeup; here's why

I would like to thank the following noders for their help on this writeup: Gritchka, for counsel in the ways of E2 etiquette; liveforever, for pointers on the history section; and Shro0m, who has an impeccable sense of HTML style, and for fixing the verb chart.


Ido is an artificial language (also known as a conlang or auxlang) that can trace its roots to Esperanto, one of the first widely adopted invented tongues. Introduced in 1887, Esperanto was the creation of Dr Ludovic Zamenhof, an oculist and amateur linguist. Zamenhof's creation was easily superior to the popular auxiliary language of the day, Volapük, and by 1900 had gathered more adherents than its competitor. While Esperanto was an advance in the field, it was still hindered by many arbitrary and unnatural features, such as special circumflexed letters, the agreement of adjectives with nouns in both number and case, and the use of the letter J to indicate plurality.

In 1907, the Delegation for the Adoption of an International Auxiliary Language, appointed a committee to find an artificial language that the Delegation could endorse as an official auxlang. The group of linguists, philosophers, and scientists concluded that only two language schemes were serious contenders: Zamenhof's unchanged Esperanto and Idiom Neutral, a refinement of the original Volapük. The full Delegation selected Esperanto as its official language, but with the major improvements of a project known only by its anonymous author's pseudonym, Ido.

With the approval of the Delegation, Louis Couturat and Louis de Beaufort, the revealed author of the Ido proposal, began work to polish the reforms of Esperanto. In addition to the problems outlined above, Couturat and de Beaufort also reworked Esperanto's rules for accusative endings and its system of derivation and affixes, with the end result of producing a much simpler and more powerful language than Esperanto in its original form.

Ido's popularity, after an initial upsurge, began to decline not long after its creation. The outbreak of World War I in 1914 dealt a severe blow to Ido; not only did the fighting consume many speakers of the new language, but Couturat, the language's unofficial leader, was killed by the car carrying the orders to mobilize the French army. Without Couturat to unite Ido's supporters, the language's followers began to splinter and bicker. The publication of several new conlangs in the years immediately following the Great War continued to divide the planned language movement in general and the Ido community specifically, further detracting from that language's popularity. In 1928, Ido suffered its worst setback since Couturat's death, the defection of Otto Jespersen, a Danish linguist and Ido's chief support among the intellectual elite, to his own auxlang, Novial.

With the popularization of the Internet, Ido and other artificial languages have enjoyed a renewed interest from the general public. Even with that new attention, the number of fluent speakers of Ido is estimated to be between 250 and 5000, while figures for the number Esperanto speakers hover around 2 million.


Unlike some languages, words in Ido are always pronounced exactly how they are spelled. There are five vowels, which are pronounced much like Japanese, Italian, and Spanish:

  • A - father
  • E - pail
  • I - Green
  • O - got
  • U - rule
Ido also has two dipthongs, AU and EU. In dipthongs, vowels combine to form new sounds, so that AU is pronounced like the OW in the English word cow, and EU sounds like the EU in the German words Heute or the OY in the English toy.

There are 23 consonant sounds in Ido:


Ido, like English, is a subject-verb-object language. Sentences in Ido correspond almost perfectly with their English translations. For example,

Ido: Pomo esas frukto.
English: An apple is a fruit.

This is makes Ido easier to learn for those raised with Western languages, since new students do not have the added confusion of an alien sentence structure, as do newcomers to languages like Japanese.

One of the things that artificial languages try to do is remove the irregularities that plague "natural" languages. Ido is no exception to this. Everything in Ido follows a pattern; for example, all verbs are regular and all nouns follow consistant patterns for number and gender. The function of a word in Ido can be easily deduced from its ending. All nouns end in O or I, adjectives end in A, adverbs end in E, and verbs have a collection of regular endings which denote tense. A complete list of affixes can be found at the end of the grammar section.


Nouns are easy to spot in Ido. If a noun is singular, it will end with an O; if it is plural, it ends with an I. Example:

Hundo = dog, Hundi = dogs
Libro = book, Libri = books
Pomo = apple, Pomi = apples

By themselves, nouns do not have a gender, like English and unlike German and Romance languages such as French and Spanish. We can refer to the doctor (doktoro) without having to specify whether the doctor is a man or a woman. Information on gender can be added, however, with the affixes -UL- and -IN-, denoting masculinity and femininity, respectively. So, doktorulo is a male doctor and doktorino is a female doctor. Notice that is it not doktoroul and doktoroin; number is the very last thing to be specified when constructing nouns.

Kuzo = cousin (non-specific), Kuzino = female cousin, Kuzulo = male cousin
Frato = sibling (non-specific), Fratino = sister, Fratulo = brother
Doktoro = doctor (non-specific), Doktorino = female doctor, Doktorulo = male doctor

There are no separate indefinite articles in Ido. They are implied with the noun, unless otherwise specified. There is, however, a definite article, LA. To take our earlier example sentences,

Pomo esas frukto = An apple is a fruit.
La pomo esas frukto = The apple is a fruit.

Hundo esas sur libro = A dog is on a book.
La hundo esas sur la libro = The dog is on the book.

This was done as a compromise between languages that have both an indefinite and a definite article, such as English, and languages with no articles, such as Russian and Japanese.


As was noted earlier, all verbs in Ido are regular. There are no exceptions to learn, unlike naturally evolved languages. Most changes to words in Ido are performed by affixes and verbs are no exception, naturally. Suffixes control tense, as well as whether the sentence is conditional or imperative.

                     To See    To Write    To Be    To Have   To Go 
Infinitive        |  vidar     skribar     esar     havar     irar 
Past              |  vidis     skribis     esis     havis     iris 
Present           |  vidas     skribas     esas     havas     iras 
Future            |  vidos     skribos     esos     havos     iros 
Conditional       |  vidus     skribus     esus     havus     irus 
Imperative        |  videz     skribez     esez     havez     irez 
Active Participles 
Past              |  vidinta   skribinta   esinta   havinta   irinta 
Present           |  vidanta   skribanta   esanta   havanta   iranta 
Future            |  vidonta   skribonta   esonta   havonta   ironta

Active participles are verbs that are being used as adjectives. In English, these end in -ing or -ed, such as "the flying birds". Some examples using the various verb forms:

La hundo iris = The dog went or the dog was going
La hundo iras = The dog goes or the dog is going
La hundo iros = The dog will go
La hundo irus = The dog would go
Irez a la hundo! = Go to the dog!

La irinta hundo = The dog that went
La hundo iranta = The dog that is going
La ironta hundo = The dog that will go

Forming additional tenses is done by adding some form of "esar" to the verb.

Me esas skribas la libro = I am writing the book.
Me esis skribis la libro = I was writing the book.
Me esos skribos la libro = I will be writing the book.

To change an active verb to a passive one, insert ES between the root word and the verb ending.

La libro skribesis = The book was being written.
La libro skribesas = The book is being written.
La libro skribesos = The book will be written.

In this way, a sentence like Ni esas trovota (We will be found) is equivalent in meaning to the shorter Ni trovesos (We will be found). In the first sentence, trovota is an adjective, specifically the future active participle, whereas in the latter sentence, trovesos is the future passive form of the verb "to find". One way of seeing the difference in meaning is that the first sentence can be translated "We will be equal to 'found'" and the second one means that "We will be found (by someone)".

Something that does not concern verbs but is rather related to them is how to negate sentences. To negate, the particle ne is placed before the verb. To use the above examples,

La hundo ne iris = The dog did not go or the dog was not going
La hundo ne iras = The dog is not going
La hundo ne iros = The dog will not go
La hundo ne irus ... = The dog would not go ...
Ne irez a la hundo! = Do not go to the dog!

Adjectives and Adverbs

Adjectives can be recognized by their A ending. They can be positioned either in front of or behind the noun they modify. The position does not change the meaning, but is done at the whim of the speaker. In general, though, shorter adjectives will precede the noun, whereas longer ones will follow.

Mikra hundo = Hundo mikra = Small dog
Granda domo = Domo granda = Big house
La libro esas bela = The book is beautiful

Superlatives and comparatives can be formed in this way:
Maxim bela = Most beautiful
Plu bela = More beautiful
Min bela = Less beautiful
Minim bela = Least beautiful
La hundo esas la minim bela. = The dog is the least beautiful.

Adverbs can be formed by replacing the A ending of adjectives with an E. Like adjectives, they may be placed before or after the modified verb. Examples of adjective to adverb changes:

Simpela (Eng: Simple) -> Simpele (Simply)
Vera (True) -> Vere (Truly)
Bona (Good) -> Bone (Well)
Rapida (Fast) -> Rapide (Quickly)


Pronouns in Ido are very similar to pronouns in English.

Eng		Subject		Object 
I/Me            Me 
You             Tu/Vu 
He              Il              Ilu 
She             El              Elu 
It              Ol              Olu 
We/us           Ni 
You             Vi 
They            Li 
One             Onu             On 
He/she/it       Lu 
Reflexive       Su 

Neccessary explanations:
  • Tu/Vu - Tu is the familiar form of the singular "you", with the same function as the German du and the Italian, Spanish, and French tu. You would address your friends and family with tu. Vu is used in more formal situations, where Sie, Lei, and usted would be used in German, Italian, and Spanish, respectively.
  • Onu/On - English speakers often use the pronoun "you" in speech to mean no one in particular, a person in general. In German, this meaning is covered by the word man, ie Man kann das sagen (One can say that). The singular onu conveys this meaning in Ido.
  • Lu - Lu is used if the speaker does not know the gender of the person or thing lu is referring to. In the previous sentence, if I had not used lu as I did, I would have had to write "he or she" or the incorrect, but commonly used, "they." Lu is singular.
  • Su - Su is used when the speaker is referring to him- or herself. Consider this example: El vidis su (She sees herself). Su refers back to the subject, el (She). Su does not vary with subject number or gender.

Since possessive pronouns are adjectives, they are formed in the same way as other adjectives in Ido; you suffix A to the pronoun. Thus,

Eng		Subject		Object 
I/Me            Mea 
You             Tua/Vua 
He              Ila             Ilua 
She             Ela             Elua 
It              Ola             Olua 
We/us           Nia 
You             Via 
They            Lia 
One             Onua            Ona 
He/she/it       Lua 
Reflexive       Sua 

Me ne havas elua libri = I don't have her books.
El ne havas sua libri = She doesn't have her books
Mea hundo havas elua libri = My dog has her books


Ido is full of ways to derive one part of speech from another. Verbs, adjectives, and nouns can all be formed from another with minimal effort.

  • Noun to adjective, adjective to noun - Adjectives and nouns can be interchanged by switching the final letter, A for adjective, O for noun. Doing this preserves the meaning of the original word.
    Noun to Adjective
    Papero (Paper) -> Papera (Something that is paper), papera chapelo = paper hat
    Metalo (Metal) -> Metala (Something that is metal), metala domo = metal house

    Adjective to Noun
    Bela (Beautiful) -> Belo (A beauty)
    Giganta (Gigantic) -> Giganto (A giant)
    Another noun-to-adjective transformation is to replace O with ALA. Unlike the O->A formation, the resulting adjective of which means "Something that is X", O->ALA results in an adjective with the meaning "Something related to X".
    Papero (Paper) -> Paperala (Something related to paper)
    Lego (Law) -> Legala (Legal, something related to the law)
    Manuo (Hand) -> Manuala (Manual, something related to hands)
  • Adjective to verb - To derive verbs from adjectives, first remove the A suffix, then add IG. From there, the desired tense can be formed by adding the necessary suffix.
    Mola (soft) -> Moligar (To soften)
    Intensa (intense) -> Intensigar (To intensify)
    Varma (warm) -> Varmigar (To warm, to make warm)
  • Verb to adjective - Adjectives can also be formed from verbs with the ALA suffix used to from adjectives from nouns, such as edukar (to educate) -> edukala (educational).
  • Verb to noun
    • Active present participles can be changed into nouns by replacing the last A with O. Nouns formed in this way mean "one who does X".
      iranta (Is going) -> iranto (One who is going)
      skribanta (Is writing) -> skribanto (A writer, one who writes)
      parolanta (Is speaking) -> parolanto (A speaker, one who speaks)
    • Gerunds are verbs that are serving as nouns in context. An example in English would be "Flying is fun". 'Flying' is normally a verb in infinitive form, but here is it a noun and the subject of the sentence. In Ido, gerunds can be formed by replacing the infinitive suffix AR with the noun-identifier O.
      Vidar (To see) -> Vido (Seeing, the act of seeing)
      Dankar (To thank) -> Danko (Thanking, the act of thanking)
      Promenar (To walk) -> Promeno (Walking, the act of walking)
      Please note that this change is totally seperate from the transforming of verbs to adjectives.
  • Noun to verb - The process for turning a noun into a verb is similar to the one for forming verbs from adjectives. Instead of IG, replace O with AG instead. This is most frequently used with tools, like a hammer.
    Martelo (A hammer) -> Martelagar (To hammer)


Forming questions in Ido is almost the mirror opposite of the same process in Japanese. In that language, a statement is transformed into a question with the suffixing of the particle ka (か) to the end of the sentence. Ido acheives the same effect by prefixing ka to the sentence.

El esas bela (She is beautiful) -> Ka el esas bela (Is she beautiful?)
Il visas elu (He sees her) -> Ka il visas elu (Does he see her?)
Me skribas (I write) -> Ka me skribas (Do I write?)


Affixes, both prefixes and suffixes, are essential to understanding Ido. Here they are, alphabetized with meaning, separated into prefixes and suffixes. Note that suffixes are not true suffixes; they are added to the root word before the true suffix, which indicates the part of speech.

  • Prefixes
    • des- The direct opposite
    • dis- Implies separation
    • ex- Retired, late
    • mi- Half
    • mis- Wrong action
    • ne- Encompasses the following English prefixes: un, im, ir, and non
    • par- Used only with verb roots to mean that an action was done thoroughly
    • pre- Before
    • pseudo- False
    • retro- Used only with verb roots to mean that the action was done backward
    • ri- Shows repetition
    • sen- Without
    • stif- Step, as in stepchild
    • vice- Deputy
  • Suffixes
    • -ach Provides disparaging meaning
    • -ad Used only with verb roots to show repeated or continued action
    • -ag Used with nouns to form verbs meaning to act with the noun
    • -aj
      • When added to an adjective or noun, denotes a thing possessing that quality
      • When added to a transitive or mixed verb, it indicates the object of the action
      • When added to an intransitive verb, it forms a noun which acts in the sense of the verb
    • -al Relating to the root word
    • -an
      • In a noun, denotes a member, inhabitant or adherent
      • In an adjective, it is used to indicate group membership
    • -ar A collection of objects
    • -ari Indicates the recipient of an action
    • -atr Like, similar to
    • -e Having the colour of
    • -ebl Encompasses the English suffixes -able and -ible
    • -ed The contents of
    • -eg To a great degreee, very large
    • -em Added to verbal roots to indicate a tendency to do an action
    • -end Something that must be done
    • -er Person which regularly performs an action
    • -eri A business
    • -es A state or quality
    • -esk To begin to
    • -esm Marks an ordinal number
    • -estr Chief
    • -et Diminutive, opposite of -eg
    • -ey A place set aside for a single purpose
    • -id Descendant
    • -ier
      • Characterised by
      • A tree or plant bearing the noun
      • A holder or container for specific purpose
    • -if Generation or production
    • -ig To render, to transform into
    • -il A tool for performing an action
    • -im Marks a numerical fraction
    • -in Female
    • -ind Worthy of
    • -ism A system or belief
    • -ist A professional
    • -iv When added to verb roots, to be capable of
    • -iz To provide or outfit with
    • -op A number in a group
    • -opl The number of times something has been done, ie once, twice
    • -oz Full of
    • -ul Male
    • -ur When added to a verb root, the product or result of the verb
    • -uy A container for
    • -yun The young of an animal

The International Language (Ido) Society of Great Britain
Hon. Secretary & Treasurer:
David Weston, 24 Nunn Street, Leek, Staffs. ST13 8EA.

Book Service Manager
Terry Minty, 44 Woodville Road, Cathays, Cardiff CF2 4EB.