# Fundamento de Esperanto: the full 1905 text online

Source: https://esperantopedia.org/about/fundamento/
Language: en
Updated: 2026-10-08

> The Fundamento de Esperanto (1905) is the unchangeable base of the language. Read its foreword, 16 rules, 42 exercises and dictionary in full.

The *Fundamento de Esperanto* ("Foundation of Esperanto") is the book of 1905 in which L. L. Zamenhof fixed the core of the language. It has four parts: a foreword, a grammar with the [16 rules](https://esperantopedia.org/grammar/16-rules/), 42 exercises and the dictionary *Universala Vortaro*. The first World Esperanto Congress made it binding in August 1905, and nobody may change it.

This section holds the whole text, copied without changes from the edition of the Academy of Esperanto.

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## Why is the Fundamento binding?

Point 4 of the Declaration of Boulogne, adopted at the first congress on 9 August 1905, names the book as the only fixed base of the language: *La sola unu fojon por ĉiam deviga por ĉiuj Esperantistoj fundamento de la lingvo Esperanto estas la verketo "Fundamento de Esperanto", en kiu neniu havas la rajton fari ŝanĝon.* – "The only foundation of the Esperanto language, binding once and for all on all Esperantists, is the little work *Fundamento de Esperanto*, in which nobody has the right to make a change."

The same point says that Esperanto has no personal legislator. Zamenhof's own opinions and later works are private and bind no one, exactly like those of any other speaker.

The base can grow, but only by addition. The [Academy of Esperanto](https://esperantopedia.org/about/academy/) adds official roots through Official Additions; it cannot alter the book. The levels of authority are explained in [official Esperanto](https://esperantopedia.org/about/official-esperanto/).

## What is in the Fundamento?

| Part | What it contains | Languages |
|---|---|---|
| [Antaŭparolo](https://esperantopedia.org/about/fundamento/antauparolo/) | Zamenhof's foreword, dated Warsaw, July 1905: why the base must stay untouchable and how the language can still grow | Esperanto |
| [Gramatiko](https://esperantopedia.org/about/fundamento/gramatiko/) | The alphabet with pronunciation hints and the 16 rules | French, English, German, Russian, Polish |
| [Ekzercaro](https://esperantopedia.org/about/fundamento/ekzercaro/) | 42 numbered exercises (§1–§42), from the alphabet to word building, each followed by its new words | Esperanto, new words in 5 languages |
| [Universala Vortaro](https://esperantopedia.org/about/fundamento/universala-vortaro/) | 2,635 roots, affixes and small words plus 298 derived words, each with five translations | Esperanto with 5 languages |

The entry counts are our own count of the Academy's edition. The Academy itself counts 2,768 "Fundamental elements" in the whole book, because it counts roots, affixes and endings from all four parts.

Apart from the foreword, the material is older than the book. The grammar comes from the [*Unua Libro*](https://esperantopedia.org/about/unua-libro/) of 1887; the dictionary and the exercises had appeared separately in 1893–1894. Hachette published the collected book in Paris in 1905.

## How do I read it here?

- **Foreword first** if you want to know why Esperanto has a fixed base; **grammar first** if you want the rules themselves.
- **Tap any word** in the foreword or the exercises. A box shows the parts of the word – root, prefix, suffix, ending – in colour, with the meaning and a link to our [dictionary](https://esperantopedia.org/dictionary/).
- **Link to a single exercise**: every § has its own anchor, for example §11, the start of the fairy tale *La feino*.
- **Look up a root**: the *Universala Vortaro* has one page per letter, and each entry links to the modern dictionary entry when we have one.

Old spellings and the 1905 translation errors stay in the text, as Zamenhof wanted. His foreword says: *La fundamento devas resti severe netuŝebla eĉ kune kun siaj eraroj* – "The foundation must stay strictly untouchable, even together with its errors."

## Is the Fundamento a good textbook?

No, and Zamenhof said so himself. The foreword states that the book "should not at all be regarded as the best textbook and dictionary of Esperanto". He recommended fuller textbooks for learning and the Fundamento as a guide to what is official.

To learn the language, start with our [course](https://esperantopedia.org/learn/course/) and the [16 rules explained in plain English](https://esperantopedia.org/grammar/16-rules/). Come back to the Fundamento when you want to check the original wording.

## Sources

- [Akademio de Esperanto – Fundamento de Esperanto (online edition)](https://www.akademio-de-esperanto.org/fundamento/)
- [David K. Jordan – The Boulogne Declaration (Esperanto text with English translation)](https://pages.ucsd.edu/~dkjordan/eo/teko/BulonjaDeklaracio.html)
- [Wikipedia – Declaration of Boulogne](https://en.wikipedia.org/wiki/Declaration_of_Boulogne)
- [Wikipedia – Fundamento de Esperanto](https://en.wikipedia.org/wiki/Fundamento_de_Esperanto)
- [Vikipedio – Fundamento de Esperanto](https://eo.wikipedia.org/wiki/Fundamento_de_Esperanto)
- [Akademio de Esperanto – Akademia Vortaro: Klarigoj](https://www.akademio-de-esperanto.org/akademia_vortaro/klarigoj.html)