The productive suffix -il- forms a noun for an instrument or means associated with an action. A tranĉilo cuts, a ŝlosilo locks or unlocks, a presilo prints, and a kuracilo is a means of treating illness. The result need not be a hand tool: it may be a machine, substance, document, computer program, or abstract aid.
English hides these relationships in unrelated words such as knife, key, printer, medicine, and form. Esperanto makes the shared function visible. The essential question is not “What object is this?” but “What action is this thing specialized for enabling or performing?”
The action before the instrument
In the regular pattern, what comes before -il- receives an action reading. The suffix is the semantic head “instrument/means,” and the base states its function:
| Action | Instrument word | Interpretation |
|---|---|---|
| tranĉi, to cut | tranĉilo | tool for cutting; knife |
| ŝlosi, to lock | ŝlosilo | tool for locking/unlocking; key |
| presi, to print | presilo | device for printing; printer |
| kompili, to compile | kompililo | program that compiles; compiler |
The final -o marks the result as a noun. Because Esperanto roots can enter different word classes, an apparently noun-like base is understood through its verbal use when -il- is added. Linio “line” has the verb linii “draw/mark lines,” so liniilo is a ruler or straightedge used for that action.
Ĉu vi vidis la ŝlosilon de la malantaŭa pordo?
Have you seen the key to the back door?
Mi bezonas akran tranĉilon por tranĉi la panon.
I need a sharp knife to cut the bread.
The instrument is normally specialized or conventionally suited to the action. A coin can happen to turn a screw, but that one use does not automatically make every coin a ŝraŭbturnilo.
More than hand tools
Devices and machines
Large or complex devices follow the same rule as simple tools.
La presilo denove ne funkcias; mi sendos la dokumenton retpoŝte.
The printer isn't working again; I'll send the document by email.
Mia malnova komputilo estas malrapida, sed ĝi ankoraŭ sufiĉas por laboro.
My old computer is slow, but it is still adequate for work.
Komputilo is a machine for komputi, originally calculating and now more broadly processing information. Its conventional scope has expanded with the technology. This is lexical development, not a change in the suffix itself.
Substances and remedies
An instrument can be material rather than mechanical. Kuracilo is anything used to cure or treat; context may make it a medicine, remedy, or therapeutic means. Solvilo can be a solvent that dissolves another substance or, figuratively, a means of solving a problem.
Ne prenu tiun kuracilon sen konsilo de kuracisto.
Do not take that medicine without a doctor's advice.
Akvo ne estas taŭga solvilo por tiu farbo.
Water is not a suitable solvent for that paint.
The negative example matters: -il- identifies function, while adjectives and context evaluate suitability, availability, or effectiveness.
Documents, software, and abstract means
A paper or digital form can enable an action. Aliĝilo is a registration form, literally a means for aliĝi “to register/join.” A retumilo is a web browser, a program used to navigate the Web. Komunikilo is any medium or means of communication.
Bonvolu plenigi la aliĝilon antaŭ vendredo.
Please fill in the registration form before Friday.
Kiun retumilon vi uzas? — Kutime tiun, kiu jam estas instalita en mia telefono.
Which browser do you use? — Usually the one already installed on my phone.
The connected exchange shows how ordinary retumilo has become. It is not limited to a physical appliance.
Scope in compounds and affix stacks
In a longer word, build the action first and add -il- to that action:
- botelo + malfermi + ilo → botelmalfermilo, bottle opener
- krajono + pintigi + ilo → krajonpintigilo, pencil sharpener
- herbo + tondi + ilo → herbotondilo, grass-cutting tool/lawn mower
La botelmalfermilo estas en la supra tirkesto.
The bottle opener is in the top drawer.
In botelmalfermilo, botelo is understood as the object of malfermi, while the entire unit botelmalferm- states the instrument's purpose. English also says “bottle opener,” but its word order should not be generalized blindly to every compound. Test the Esperanto paraphrase: ilo por malfermi botelojn.
Affix order can make the causal structure explicit. Pint-ig-il-o is an instrument for making something pointed. Here -ig- first forms the action pintigi, and -il- then forms its instrument. Moving the pieces would change or obscure that relationship.
La krajonpintigilo estas plena; malplenigu ĝin antaŭ ol uzi ĝin denove.
The pencil sharpener is full; empty it before using it again.
The affix stacking and scope page explains how each rightward step takes the preceding unit into its scope.
Instruments that act and instruments that users act with
Usually the user performs the base action by means of the instrument: a person tranĉas per tranĉilo. Sometimes the instrument itself is presented as performing the action. A sonorilo is something that sonoras “rings”; the user sonorigas ĝin “makes it ring.”
La sonorilo sonoris ĝuste je la oka.
The bell rang exactly at eight.
This is a conventional and fully regular perspective: -il- names an instrument defined by the event it produces, even when the agent's corresponding verb contains -ig-.
Some established words contain an understood action rather than an overtly ordinary verb base. Fajrilo is a lighter, a tool for making fire, not normally “a tool for fajri.” Diskilo conventionally means a disk drive/device that reads or writes disks. PMEG recommends restraint with such compressed formations because the missing relationship can be unclear in a new coinage.
Not every tool needs -il-
Many instrument names are simple roots: martelo “hammer,” forko “fork,” kulero “spoon,” broso “brush,” gitaro “guitar,” and biciklo “bicycle.” Adding -il- to a word that already names the instrument is normally redundant or changes the analysis.
Prenu martelon, ne ŝraŭbturnilon; ĉi tie estas najlo.
Take a hammer, not a screwdriver; there is a nail here.
The productive system helps create missing or general terms; it does not require all tools to display the same suffix. Likewise, manĝilo is the general category “eating utensil,” not the ordinary word for every individual fork or spoon and certainly not “food.” Food is manĝaĵo.
La apartamento havas telerojn, sed ni devas aĉeti manĝilojn.
The apartment has plates, but we need to buy cutlery.
Where -il- is too broad, a transparent compound can be more precise: presmaŝino, solvosubstanco, or kompilprogramo. Such alternatives are especially useful in (technical) writing, where the physical or software category matters.
Conventionality and responsible coinage
The Fundamento gives -il- its instrument sense, and present-day Esperanto uses it freely. Yet convention can override a mechanically expected analysis. Armilo conventionally means a weapon, although the verb armi means “equip with weapons,” which could suggest an instrument for arming. Established usage wins. Aviadilo remains the normal word for an aircraft even though alternatives such as avio also occur.
Pedagogical recommendation: derive from a recognizable action whenever possible. If the relation is compressed, novel, or technical, use a clearer compound or explain it at first mention. Consult actual usage rather than assuming that every English -er noun maps to -ilo; English teacher, for example, names a person and requires instruisto, not an instrument suffix.
Common Mistakes
1. Adding -il- to a word that already names a tool.
❌ Mi batis la najlon per martelilo.
Incorrect in the ordinary meaning: martelo already means ‘hammer.’
✅ Mi batis la najlon per martelo.
I struck the nail with a hammer.
2. Confusing a means of eating with food.
❌ La supo estas bongusta manĝilo.
Incorrect: manĝilo is an eating utensil, not something eaten.
✅ La supo estas bongusta manĝaĵo.
The soup is tasty food.
3. Reversing the semantic order of a compound.
❌ Mi ne trovas la malfermbotelilon.
Incorrectly structured for ‘bottle opener’: the bottle is what gets opened.
✅ Mi ne trovas la botelmalfermilon.
I can't find the bottle opener.
4. Assuming every thing temporarily used for an action is conventionally an -ilo.
❌ Ĉiu monero, per kiu eblas turni ŝraŭbon, estas ŝraŭbturnilo.
Incorrect generalization: accidental use does not make every coin a screwdriver.
✅ Mi uzis moneron kiel provizoran ŝraŭbturnilon.
I used a coin as a makeshift screwdriver.
Key Takeaways
- -il- makes an instrument or means the semantic head; the preceding unit supplies its function.
- The regular input is an action, even when the visible root is familiar as a noun or adjective.
- Instruments include tools, machines, substances, documents, programs, and abstract means.
- Build compounds as “instrument for doing X,” and keep affix scope explicit.
- Established simple roots and lexicalized forms remain part of the language; morphology is productive, not compulsory.
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Start learning Esperanto →Related Topics
- Root Character and CategoryA2 — Understand how a root's inherent meaning shapes its noun, adjective, adverb, and verb forms.
- Compound Head OrderA2 — Interpret and build ordinary Esperanto compounds with the general head on the right and its modifier before it.
- Affix Stacking and ScopeB2 — Interpret and build multi-affix Esperanto words by applying each layer in order and keeping the semantic head and participant roles clear.
- Lexicalization and ConventionalityB2 — Understand why structurally transparent Esperanto words develop conventional meanings that cannot be predicted from morphology alone.
- Coining Understandable New WordsB2 — Create transparent Esperanto words by choosing a clear semantic head, explicit relation, economical structure, and a form that listeners can interpret without private guesswork.