Akademio de Esperanto: the Fundamento and official words

The Academy of Esperanto (Akademio de Esperanto) is an independent body of language experts that guards the Fundamento de Esperanto of 1905 and decides which new roots become official. It began as the Language Committee (Lingva Komitato), created at the first World Esperanto Congress in Boulogne-sur-Mer in 1905, and has had its present name since 1948. In June 2026 it had 43 members and 9 correspondents. It advises and recommends; it cannot punish anyone for how they speak.

#What does the Academy of Esperanto do?

Its statute gives it two aims: to preserve and protect the fundamental principles of Esperanto, and to monitor how the language develops. In practice it:

• decides questions of usage, such as what a grammatical form means or how a word is built;
• adds roots to the official vocabulary through the Oficialaj Aldonoj (Official Additions);
• compiles a dictionary with definitions in Esperanto and approves technical glossaries;
• answers questions from the public through its Language Consultancy (Lingva Konsultejo), founded in 1999.

The Academy has its legal seat in the Netherlands and is funded by a subsidy from the Universal Esperanto Association plus donations. For the other bodies of the movement, see Esperanto organizations.

#How is the Academy organised?

The Academy has about 45 members who serve nine-year terms, work in specialist sections and vote openly on language questions. The statute sets the rules.

The Indian linguist Probal Dasgupta, president from 2016, died on 1 June 2026. The Academy's board page, updated in October 2026, lists Jesper Jacobsen as president.

#What is the Fundamento de Esperanto?

The Fundamento de Esperanto is the book Zamenhof published in 1905 to fix the core of the language. It has four parts: a foreword (Antaŭparolo), the grammar (Gramatiko) with the 16 rules, the exercises (Ekzercaro) and the dictionary Universala Vortaro. Grammar and dictionary give translations in five languages: French, English, German, Russian and Polish. Most of the content comes from Zamenhof's earlier works, above all the Unua Libro of 1887. The full text, with every Esperanto word explained, is in our Fundamento de Esperanto section.

On 9 August 1905 the Declaration of Boulogne, adopted at the first congress, named the Fundamento as the only basis binding on all Esperantists. It cannot be changed, and no person, Zamenhof included, has legislative authority over the language. The foreword already expected that some authoritative institution would later add new words. That is the Academy's role.

The Academy counts 2,768 Fundamental elements (roots, affixes, small words and endings): 2,755 plus 13 whose Fundamental status it confirmed in 1974. The old translations contain mistakes that remain in the untouchable text. The Language Committee prepared corrections in 1906–1913 and published them in 1922–1923 as the Akademiaj Korektoj; the Academy's dictionary uses them.

#What are the Official Additions (1OA–10OA)?

An Official Addition (Oficiala Aldono, OA) is a list of roots that the Language Committee or the Academy adds to the Universala Vortaro. The first six were decisions of the Committee. "Official" does not mean "Fundamental": the Academy writes that an official root has the character of a strong recommendation, because only elements of the original Fundamento are Fundamental.

Three single decisions added one element each: analog- (1923), mis- (1929) and end- (1953). The 10th Addition was approved on 24 September 2023: 41 of the 45 members voted, with 32 in favour, 4 against and 5 abstaining. It made official all country names from the 2009 list that were not yet official, plus South Sudan, and for the first time multi-word names such as la Ruĝa Maro – "the Red Sea".

#The official vocabulary in numbers

The Academy's dictionary, the Akademia Vortaro, counts 4,953 official elements up to the 9th Addition (2007): 2,768 Fundamental and 2,185 official (1,776 from 1909–1958, plus 200 and 209). Of these, 4,758 need an ending (roots and affixes), 184 are standalone small words and 11 are grammatical endings. Adding the 420 roots of 2023 gives about 5,373 – our own sum, because the Academy's statistics table stops at 2007. Our list of official roots has 5,328, because it counts one root per entry marked as official in the ReVo dictionary, not the Academy's elements.

These numbers are a small part of the vocabulary. Most everyday and modern words are not on the official list, but they are normal Esperanto: see word building. Other projects count differently; the statistics page of the ReVo dictionary, for instance, lists 860 roots for the first Addition instead of 805.

#What is the Baza Radikaro Oficiala (BRO)?

The Baza Radikaro Oficiala ("Official Basic Roots"), or BRO, is the Academy's ranking of the core vocabulary in nine frequency groups. The Academy worked on it from 1966 and published it in Aktoj de la Akademio II (1968–1974), together with the 8th Addition.

Method. The Academy compared earlier word-frequency studies: S. Rublev (1927, 100,000 words of running text), L. Blaas (50,000 words), three lists by V. Setälä, a 1956 list by P. Bovet and H. Ith, and two lists of the French Français fondamental. An element found in every list went to group 1, one missing from a single list to group 2, and so on down to group 9 for elements found in only one list. The raw result was 2,537 elements; after corrections the final groups hold 2,461 (our sum of the Academy's group counts).

179

101

121

151

154

241

294

467

753

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Show the data

Group	Elements	Running total
1	179	179
2	101	280
3	121	401
4	151	552
5	154	706
6	241	947
7	294	1,241
8	467	1,708
9	753	2,461

Group 1 has no ordinary noun or verb roots at all. It consists of the 11 endings, the participle suffixes, pronouns, numerals, table words such as kio and tiu, common affixes and small words such as kaj and de. The Academy calls the list a help, not a law, and suggests that a textbook may include, for example, the first four groups. The source lists date from 1927–1956, so BRO shows older frequency; for modern counts see the 100 most common Esperanto words. The Akademia Vortaro can be searched by BRO group (BRO1–BRO9).

#Which Academy decisions matter most?

#What are the limits of the Academy?

It advises. Statute article 22 allows decisions that are only recommendations, and the Academy states that it can neither compel nor wants to compel language use. Answers from its Language Consultancy are recommendations, not decisions.

Usage decides first. Grammar writer Bertilo Wennergren notes in PMEG that new ordinary roots enter the language easily, while new affixes rarely succeed. A word missing from the official list is not an error.

It is slow and partial. Sixteen years passed between the 9th and 10th Additions (2007–2023), and also between the 7th and 8th (1958–1974). The 9th and 10th give no translations, so learners still need a bilingual dictionary; the Academy argues that the language is mature enough to define itself.

Voting is contested. In 1953 the writer Petro Stojan argued that votes on language problems let many non-experts overrule two or three real experts. The statute adds safeguards: sections prepare reports, and changes to earlier decisions need two thirds of all members. In 2003 the Academy reversed itself on Koreo and Egipto, which shows that its rulings can be revised.

#Common questions

#Who decides what is correct Esperanto?

The Fundamento of 1905 is the only binding authority, and the Academy interprets it and recommends usage. Beyond that, correctness comes from good usage by competent speakers, with reference works such as the PMEG grammar.

#Can the Academy change the Fundamento?

No. The Declaration of Boulogne made the Fundamento unchangeable on 9 August 1905. The Academy can only add roots through Official Additions and recommend usage; even known translation errors stay in the text and are corrected in separate documents.

#How many official roots does Esperanto have?

The Academy counts 4,953 official elements up to 2007 (2,768 Fundamental, 2,185 from Official Additions). The 420 roots of 2023 bring the total to about 5,373 elements, almost all of them roots or affixes that take an ending.

#Is a word wrong if it is not in the Academy's dictionary?

No. The official list is a core, not a complete vocabulary. Many standard words in large dictionaries are not official, and the Academy itself calls even its official roots strong recommendations, not commands.

#Does the Academy allow the x-system?

In effect, yes, as a technical substitute. The 2007 statement does not name the x-system, but it permits replacing letters with diacritics by other characters when this is only a technical aid, aims at no spelling reform and causes no confusion.

#Sources

• Akademio de Esperanto – Statuto
• Akademio de Esperanto – Historio de la Akademio
• Akademio de Esperanto – Membroj kaj korespondantoj (June 2026)
• Akademio de Esperanto – Sekcioj kaj Komisionoj (March 2025)
• Akademio de Esperanto – Estraro kaj adreso (October 2026)
• Akademio de Esperanto – Omaĝo al Probal Dasgupta
• Akademio de Esperanto – Lingva Konsultejo
• Akademio de Esperanto – Akademia Vortaro: Klarigoj (statistics)
• Akademio de Esperanto – Fundamento
• Akademio de Esperanto – Naŭa Oficiala Aldono (2007)
• Akademio de Esperanto – Deka Oficiala Aldono (2023)
• Akademio de Esperanto – Baza Radikaro Oficiala (Aktoj II, 1968–1974)
• Akademio de Esperanto – Pri apartaj teknikaj bezonoj rilate al niaj alfabeto kaj ortografio (2007)
• Akademio de Esperanto – Pri la vortoj KOREO kaj EGIPTO (2003)
• Akademio de Esperanto – Listo de Rekomendataj Landnomoj (2009)
• Akademio de Esperanto – Pasivaj participoj (1967, 1989)
• Akademio de Esperanto – Deklaro pri la litero ŭ (2023)
• Akademio de Esperanto – Pri la esprimo "tiel nomata" (2026)
• Vikipedio – Akademio de Esperanto
• Vikipedio – Oficialaj aldonoj
• Vikipedio – Baza Radikaro Oficiala
• Vikipedio – Fundamento de Esperanto
• Vikipedio – Akademiaj Korektoj
• Wikipedia – Akademio de Esperanto
• Wikipedia – Fundamento de Esperanto
• Wikipedia – Declaration of Boulogne
• Wikipedia – Probal Dasgupta
• PMEG – Neoficialaj afiksoj
• ReVo – Statistiko
• Libera Folio – 10-a Oficiala Aldono al la Universala Vortaro