Kilo Lingo
Esperanto grammar Part of Chapter 19

CEFR B1-B2

4 min read

Test yourself (27 questions)

Esperanto Affixes That Are Also Words: ilo, aro, eta, igi

By Michael McGettrickUpdated 12 October 2026

Most Esperanto affixes are words in their own right: give -- an ending and you have , a tool. So a long word holds nothing but words. Two traps sit at the edges: some prefix-like pieces are ordinary roots (-, -), and some words only look built ().

affixordinary root doing affix workthe endingWhat do the colours mean?
PieceAs a wordEnglish
--a tool
--a group, a set
--slight, small
--to cause, to make
-vice-president ()
looks builta mistake: one root

Quick check

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

Pick the right one

0/3

Built from pieces, or one root that only looks built? If the pieces give the wrong meaning, it is one root.

  1. vortaro

  2. eraro

  3. lernejo

Affixes standing alone

affixthe endingWhat do the colours mean?

Put an ending on an affix and it behaves like any root. Dictionaries list these as words; some are everyday vocabulary, some rarer:

AffixWordEnglish
--a tool
--a group, a set
--a member
--an offspring
--a head, a boss
--a person, a guy
--a bit, a particle
--a quality
--slight, small
--huge
--possible
--to cause, to make
--to become
-on the contrary
  • a toola tool
  • a groupa group
  • smallsmall

They work in sentences like any other word:

  • . - I need the right tool.
  • . - That made me think.
  • . - It suddenly turned cold.
  • . - That is not possible.
  • , ! - On the contrary, I like it!

Not every affix makes a useful word: the pet-name suffixes -- and -- are almost never seen alone. The common ones are plain vocabulary, the kind you will write this week.

Affixes on affixes

affixthe endingWhat do the colours mean?

An affix used as a word takes affixes like any root, so a word can be built with no root in it at all:

ilo, a tool; ilaro, a set of tools: a toolkit
WordPiecesEnglish
-- + --a toolkit
-- + --a possibility
-- + --a board, a committee
-- + --the membership
  • o. - There is only one possibility.

This is the promise behind reading a long word from the right: every piece is a word you can look up. is not, healthy, person, place: a hospital.

Roots doing affix work

official prefixordinary root or small wordWhat do the colours mean?

PMEG counts ten official prefixes: - ĉef- - - - - - - - -. Many textbooks add -, which the has only as an exclamation, and ĉef- doubles as an ordinary root (, main). Anything else at the front of a word is an ordinary root or small word, which compounding allows for any root:

WordFirst pieceEnglish
prefix -a father-in-law
prefix -parents
prefix -an ex-husband
, a turna vice-president
, withoutlimitless
for, awayto go away
, samea fellow
, halfhalf an hour

The same happens at the back. Some roots are so common as the last piece that they feel like suffixes, but they are still roots and behave like them:

WordLast pieceEnglish
, fullcrowded
, similarhumanlike
ideoriĉa, richrich in ideas
  • . - The hall was crowded.

International endings such as -ologio are not on the official list either: came into Esperanto as a whole word. Unofficial affixes covers where -olog- does and does not work.

Words that only look built

affixWhat do the colours mean?

Once you can take words apart, you will try it on words that are not built. The test is the meaning: if the pieces give a meaning the word does not have, the word is one root.

WordFalse splitReal meaning
+ + o: bitsa mistake
+ : neck golda colour
+ : valley golda value
+ roa centre
  • . - I made a mistake.

only looks built too: it is one root, -, a colleague. Split as it would be a huge neck, which is not what the word means. A dictionary files each word under its own root: under -, under -.

Mistakes English speakers make

WrongRightWhy
. .-- takes an object; -- never
as -o, one rootthe split gives the wrong meaning

What to do next

  1. Use , and in a sentence each today.
  2. Next time a long word stops you, split it from the right and check each piece is a word.
  3. Then read compounding for how roots join.

See also

Practise: test yourself

Matching

0/6

Each of these is an affix used as an ordinary word. Match it to its meaning.

Sort into groups

0/8

Is the first piece an official prefix, or an ordinary root or small word?

Tap a word, then the group it belongs in.

Pick the right one

0/8

Built from pieces, or one root that only looks built? If the pieces give the wrong meaning, it is one root.

  1. vortaro

  2. eraro

  3. lernejo

  4. koloro

  5. internacia

  6. valoro

  7. kunveno

  8. centro

Build the word

0/3

Build the word from its pieces.

  1. a toolkit (tool + set)

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

    Your word is empty.

  2. a possibility (possible + quality)

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

    Your word is empty.

  3. the capital city (main + city)

    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.

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Frequently asked questions

Can Esperanto affixes be used as words on their own?
Most of them, yes. Give an affix an ending and it behaves like any root, and dictionaries list the results as ordinary words: (a tool), (a group), (a member), (a boss), (a guy), (slight), (huge), (possible), (to cause), (to become). is I need a tool; is that made me think.
Is vic- an official Esperanto affix?
No. Vic- is an ordinary root (, a turn or a row) used at the front of a compound, which the compounding rule allows for any root: , vice-president. Ĉef- is the borderline case: PMEG counts it among the ten official prefixes (bo-, ĉef-, dis-, ek-, eks-, ge-, mal-, mis-, pra-, re-), yet it is just as often an ordinary root (, main). Many textbooks also list fi-, which the has only as an exclamation. The words behave the same either way: only the bookkeeping differs.
What is an Esperanto word with no root in it?
A word built only from affixes and an ending. is -il- plus -ar-: a set of tools, a toolkit. o is -ebl- plus -ec-: a possibility. is -estr- plus -ar-: a board or committee. It works because every one of those affixes is a word already.
Why is not a collection of fragments?
Because it is one root, erar-, and its likeness to er- plus -ar- is a coincidence. The test is the meaning: a set of fragments is not a mistake, so the split is wrong. is not plus (neck gold) and is not plus (valley gold). A dictionary settles it in seconds: sits under its own root.
Are -ologio and -fobio Esperanto affixes?
They are not on the official list. Words like came into Esperanto whole, as international words, and that is how to learn them. Some writers treat -olog- and -ologi- as unofficial suffixes for fields that already have an international name; the unofficial affixes article covers where that works and where it does not.