Kilo Lingo
Esperanto grammar Part of Chapter 25

CEFR B2-C1

5 min read

Test yourself (23 questions)

Scientific Esperanto: The Register That Almost Won

By Michael McGettrickUpdated 12 October 2026

Scientific words come into Esperanto whole and then take Esperanto endings: gives and o. The -ik- and -ologi- inside them are mostly not suffixes you may reuse. And the history is short: Esperanto never became the language of science, but it produced the man who organised science's vocabularies.

Esperanto affixEsperanto endingWhat do the colours mean?
WordEnglishHow it got there
chemistryimported whole
chemical + Esperanto -a
kemiistoa chemist + --
theatricalnot teatricala
biologywhole: -ologio is no suffix
orelitoear infection--: medicine only

Quick check

Now use it: three quick questions on the chart above. The full practice is further down.

Pick the right one

0/3

True or false?

  1. Biologio is an official Esperanto compound of bio + logio.

  2. Rule 15 says to import an international word whole.

  3. Esperanto reads -ik- as a suffix in every word that ends in it.

Rule 15: import whole, then derive

Esperanto affixEsperanto endingWhat do the colours mean?

Rule 15 of the , in its own English column:

The so-called "foreign" words, i. e. words which the greater number of languages have derived from the same source, undergo no change in the international language, beyond conforming to its system of orthography. Such is the rule with regard to primary words, derivatives are better formed (from the primary word) according to the rules of the international grammar, e. g. o, "theatre", but a, "theatrical", (not teatrical'a), etc.

Two steps. Import the base word whole, in Esperanto spelling:

EsperantoEnglish
chemistry
biology
psychology
galaxy
gene
laboratory

Then derive with Esperanto, never with the source language:

  • . - The chemistry laboratory is big.
  • . - She is a scientist.
  • . - That is a biological question.

If you have read science in a European language, you already know hundreds of these roots.

Looks like a suffix, is not one

a real suffixWhat do the colours mean?

Learners who know - and - see and expect an -ologio suffix. Mostly there is none: the words came in whole, as affixes as words explains.

EndingReal suffix?Example
-ik-no: leave these words e,
-olog-, -ologi-narrowly, where an international word existskancerologo
-fobio, -no: these words came in wholetermometro
-oz-in medicine: a diseasetuberkulozo
--in medicine: an inflammationorelito

-ik- is the trap. names a field, but is traffic and is a sleeve. Reading -ik- as a suffix would make dozens of words seem to mean something else, so PMEG's advice is : leave these international words in peace.

-olog- works only narrowly. PMEG says it is used almost only where a matching international word exists: kancerologo for an oncologist. Do not invent an -ologio for cookery.

-- is for medicine. Orelito is an ear inflammation. In everyday language PMEG prefers the plain word: inflamo.

-eno: dodging -in-

-- makes a female, so an imported word ending in - can look like a female form. For some words, Esperanto chose -eno instead:

WordEnglish
a donkey
delfenoa dolphin
ermenoan ermine
tendenoa

Platinum is both plateno and o, and PMEG calls both perfectly good words. Not every - changed: in , , and , medicine, the -- is only a look-alike inside a single root.

The 1922 report

In 1922 the League of Nations adopted a report on Esperanto. It was friendly, and it was candid about the gap:

What it still lacks is technical vocabularies for several important sciences. There already exist Esperanto vocabularies for chemistry, pharmaceutics, mechanics, navigation and botany, but there are not any for electricity, physics and geology. The Esperanto Academy should have these vocabularies prepared at once. The lack of financial resources seems to have been the chief cause of this delay.

The same report records the petition that later accounts inflate:

A petition was presented in 1921 by 25 members of the French Academy of Science asking that Esperanto should be taught in technical schools.

That is a petition about teaching in technical schools, not a call for Esperanto as the language of science.

  1. 1904Internacia Scienca Revuo founded

  2. 1906ISAE, the scientific association

  3. 1922the League of Nations report

  4. 1949Scienca Revuo begins

  5. 2015Scienca Revuo stops

Wüster and terminology science

Eugen Wüster (1898 to 1977) compiled a large Esperanto-German dictionary as a student, between 1918 and 1920. His later work on standardising technical vocabulary made him the founder of modern terminology science:

YearWhat Wüster did
1931published his book on technical language standards
1951took over the ISO terminology committee's secretariat
1971started Infoterm, the terminology centre

He also coined two words the movement still uses: esperantologio, the study of Esperanto, and , a planned language. Esperanto did not become the language of science; one of its dictionary-makers organised how science names things.

What you can read today

Popular science, yes; original research, essentially no.

SourceWhat it isAlive?
monthly magazine, Antwerp, since 1980yes: science column
Vikipediothe Wikipediayes
the scientific association's journalno: since 2015
  • 2015. - The journal has not appeared since 2015.

For a learner, and Vikipedio are the reading list: plain, factual prose on every subject. The Esperanto today article has the wider picture.

Mistakes English speakers make

WrongRightWhy
teatricaladerive with endings
biologika + -a, no -ical
one imported root, not two pieces
kuirologiono international word to copy

What to do next

  1. Take five science words you know in English and find their Esperanto forms.
  2. Build the adjective and the person for each: , o.
  3. Then read measurements for units and numbers aloud.

See also

Practise: test yourself

Sort into groups

0/8

Did the word come in whole, or was it built in Esperanto?

Tap a word, then the group it belongs in.

Build the word

0/3

Build the word from its pieces.

  1. theatrical (from teatro)

    Accents optional - cx, gx, ux work for ĉ, ĝ, ŭ

    Your word is empty.

  2. a scientist (from scienco)

    Accents optional - cx, gx, ux work for ĉ, ĝ, ŭ

    Your word is empty.

  3. chemical (from kemio)

    Accents optional - cx, gx, ux work for ĉ, ĝ, ŭ

    Your word is empty.

Spot the mistake

0/2

Each sentence has one wrong word. Tap it.

Pick the right one

0/5

True or false?

  1. Biologio is an official Esperanto compound of bio + logio.

  2. Rule 15 says to import an international word whole.

  3. Esperanto reads -ik- as a suffix in every word that ends in it.

  4. Azeno ends in -eno so that it does not look like a female form.

  5. Scienca Revuo still appears every quarter.

Matching

0/5

Match each name or date to what it is.

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Frequently asked questions

How do scientific words get into Esperanto?
Whole, under Rule 15 of the : an international word keeps its form, adjusted only to Esperanto spelling, and derivatives are then built with Esperanto grammar. The rule's own example is , theatre, with the adjective , not teatricala. So gives and kemiisto.
Are -ologio and -fobio Esperanto suffixes?
Not official ones. , and similar words came in whole. PMEG treats -olog- as an unofficial suffix used almost only where a matching international word exists, as in kancerologo for an oncologist. Do not coin new -ologio words for fields that have no international name, and for a new measuring device PMEG prefers -mezurilo (pluvomezurilo) to -metro: build with Esperanto roots instead.
Why do some Esperanto animal words end in -eno?
To dodge the suffix -in-, which makes a female. PMEG notes that some international words took -en- where the source had -in-, so that they would not look like a female form: (a donkey), delfeno (a dolphin), tendeno (a ). Plateno and platino, platinum, are both good words.
Can you read science in Esperanto today?
Popular science, yes. The monthly , published in Antwerp since 1980, has a science column, and the Esperanto Wikipedia has a large body of plain non-fiction. Original research is another matter: the scientific association's journal, , has not appeared since 2015.
Who was Eugen Wüster?
An Austrian engineer and industrialist (1898 to 1977) who compiled a large Esperanto-German dictionary as a student, between 1918 and 1920. His later work on technical vocabulary made him the founder of modern terminology science: he took over the secretariat of the ISO terminology committee in 1951 and started Infoterm in 1971. He also coined the words esperantologio and .