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Grammar

The 16 rules of Esperanto grammar, explained

The official core of Esperanto grammar: short, written in the 1880s and still valid today.

Updated: 6 min read

The 16 rules are the grammar section of the Fundamento de Esperanto, the 1905 book that defines the language. L. L. Zamenhof first published them in the Unua Libro, which appeared in Russian in Warsaw on 26 July 1887. Together they cover endings, tenses, pronouns, stress and a few general principles.

The rules are binding but not complete. The Declaration of Boulogne (1905) made the Fundamento untouchable: nobody may change it, although new words and official decisions can be added.

The official text exists in French, English, German, Russian and Polish. Esperanto translations exist, but they are not part of the Fundamento.

Before the rules: the alphabet

The grammar opens with the 28-letter alphabet, one sound per letter, including ĉ, ĝ, ĥ, ĵ, ŝ and ŭ. Two notes follow: ŭ is used only after vowels, and printers without accented letters may write ch, gh, hh, jh, sh, u instead. Full guide: the Esperanto alphabet.

Parts of speech (rules 1–8)

Rule 1: the article

There is one article, la – "the", the same for every gender, number and case. There is no indefinite article, so domo means "a house". The rule even lets beginners leave la out at first. More: the article la.

Rule 2: nouns

Nouns end in -o, and the plural adds -j. There are only two cases: the basic form and the accusative with -n. Other relations use prepositions: patro – "father", patroj – "fathers", patron – "father" (as object), de la patro – "of the father", al la patro – "to the father".

Rule 3: adjectives

Adjectives end in -a and take -j and -n like nouns. Comparison uses pli – "more", plej – "most" and ol – "than": pli blanka ol neĝo – "whiter than snow". More: nouns and adjectives.

Rule 4: numbers

The basic numbers are unu, du, tri, kvar, kvin, ses, sep, ok, naŭ, dek, cent, mil (1–10, 100, 1000). Larger numbers are joined from these: kvincent tridek tri – 533. Endings and suffixes make ordinals (kvara – "fourth"), multiples (-obl-), fractions (-on-) and groups (-op-), and po shows distribution: po kvin – "five each".

Rule 5: pronouns

The personal pronouns are mi, vi, li, ŝi, ĝi, si, ni, ili, oni. Adding -a makes the possessive, mia – "my", and pronouns take -n like nouns: min – "me". More: pronouns.

Rule 6: verbs

Verbs never change for person or number. Six endings do all the work: -i infinitive, -as present, -is past, -os future, -us conditional, -u command or wish. Six participles (-ant-, -int-, -ont-, -at-, -it-, -ot-) express active and passive meaning.

The passive is esti plus a passive participle, with de for "by": ŝi estas amata de ĉiuj – "she is loved by everyone". The English text of 1905 calls -us the "subjunctive"; today it is called the conditional. More: verbs.

Rule 7: adverbs

Adverbs end in -e and compare like adjectives: mia frato kantas pli bone ol mi – "my brother sings better than I do".

Rule 8: prepositions

Prepositions are followed by the basic form (the nominative): kun la patro – "with the father". The systematic exception is rule 13, where -n after a preposition of place shows direction.

General rules (rules 9–16)

Rule 9: reading

Every word is read exactly as it is written. There are no silent letters.

Rule 10: stress

Stress always falls on the second-to-last syllable: fa-mi-li-o, es-pe-ran-to.

Rule 11: compound words

Compounds are made by simply joining words, with the main word last: vaporŝipo – "steamship" (vapor- "steam" + ŝip- "ship"). The 1905 text marks word parts with apostrophes for learners (patr'o), a practice no longer used. More: word building.

Rule 12: negation

One negative per clause is enough. If the clause has another negative word, ne is left out: mi neniam vidis – "I have never seen", mi nenion vidis – "I saw nothing".

Rule 13: direction

To show movement towards a place, a word takes -n: kie? – "where?", kien? – "where to?"; tie – "there", tien – "to there"; mi iras Parizon – "I am going to Paris". Today al Parizo is more usual. More: the accusative.

Rule 14: the preposition je

Every preposition has a fixed meaning. When none fits, use je, which has no meaning of its own: ĝoji je tio – "to be glad about that". The accusative without a preposition can replace je: ĝoji tion.

Rule 15: foreign words

International words take Esperanto spelling and nothing else. Only the base word is borrowed; related words are built with Esperanto endings: teatro – "theatre", teatra – "theatrical".

Rule 16: the apostrophe

The final -o of a noun and the -a of la may be dropped and replaced with an apostrophe: de l' mondo – "of the world". Today this happens almost only in poetry and songs.

What the 16 rules leave out

The rules were written in the 1880s, in a traditional style and from a European point of view. PMEG's commentary calls the belief that Esperanto has only 16 rules a common misunderstanding. Topics they barely touch or skip:

  • the 45 correlatives (kiu, tiu, ĉiu…) and the meanings of prefixes and suffixes, which appear in the Fundamento's dictionary and exercises instead;
  • word order, yes/no questions with ĉu, and clauses with ke – "that";
  • when to use the reflexive si instead of li or ŝi;
  • the accusative for dates and measures (lundon – "on Monday", du horojn – "for two hours");
  • what time the participles express, settled by the Akademio de Esperanto in decisions of 1967 and 1989;
  • how the suffixes -ig- and -iĝ- switch verbs between transitive and intransitive.

Where to find the full grammar

  • PMEG (Plena Manlibro de Esperanta Gramatiko) by Bertilo Wennergren: the most complete free reference, online since 1995, written in Esperanto. Version 15.5 dates from June 2024.
  • The Fundamento itself: besides the rules, its Ekzercaro (exercises) and Universala Vortaro (dictionary) show the grammar in use.
  • Decisions of the Akademio de Esperanto: official clarifications, for example on participles.

Examples in sentences

  • La libro estas sur la tablo. – "The book is on the table."
  • Mi vidas du katojn. – "I see two cats."
  • La bluaj floroj estas tre belaj. – "The blue flowers are very beautiful."
  • En la klaso estas dudek tri lernantoj. – "There are twenty-three pupils in the class."
  • Ŝi skribis al mi longan leteron. – "She wrote me a long letter."
  • Hieraŭ mi laboris, hodiaŭ mi ripozas. – "Yesterday I worked; today I'm resting."
  • Li kuras rapide. – "He runs fast."
  • Ni veturos al la maro per trajno. – "We'll go to the sea by train."
  • Mia avino havas grandan legomĝardenon. – "My grandmother has a big vegetable garden."
  • Hodiaŭ neniu venis. – "Nobody came today."
  • La infanoj kuris en la parkon. – "The children ran into the park."
  • Mi venos je la tria. – "I'll come at three."

Common questions

Does Esperanto really have only 16 grammar rules?

No. The 16 rules are the official core, but they leave out word order, the correlatives, the use of si and much more. Complete grammars such as PMEG run to hundreds of pages.

Who wrote the 16 rules, and when?

L. L. Zamenhof, the creator of Esperanto. They first appeared in the Unua Libro in 1887 and became part of the Fundamento de Esperanto in 1905.

Can the 16 rules be changed?

No. Since the Declaration of Boulogne (1905), the Fundamento may not be changed. The Akademio de Esperanto can add words and issue decisions, but it cannot rewrite the rules.

Is there an official Esperanto version of the 16 rules?

No. The official texts are in French, English, German, Russian and Polish. Esperanto translations, for example in PMEG, have no official status.

Sources

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