English “twice” can mean either “multiplied by two” or “on two occasions.” Esperanto normally keeps those meanings apart. The official suffix -obl- expresses multiplication or a multiple: duobla, duoble, duoblo. The noun fojo and its compounds count occasions: du fojojn, dufoje, dufoja.
Multiplication with -obl-
Attach -obl- to a number and choose a normal ending:
| Form | Function | Example meaning |
|---|---|---|
| duobla | adjective | double; multiplied by two |
| duoble | adverb | twofold; by a factor of two |
| duoblo | noun | a quantity twice as large |
La firmao proponis duoblan pagon por la nokta deĵoro.
The company offered double pay for the night shift.
La nova baterio daŭras trioble pli longe ol la malnova.
The new battery lasts three times as long as the old one.
Kvindek estas la kvinoblo de dek.
Fifty is five times ten.
The number states the multiplication factor. Triobla prezo is a price equal to three times the reference price; it is not a price charged on three separate occasions.
An -obl-a word can also describe something made of that many corresponding layers or parts:
La apartamento havas duoblajn fenestrojn, do la strato apenaŭ aŭdiĝas.
The apartment has double windows, so the street is barely audible.
This extension still contains the idea of doubling: two layers or matching components function as one unit.
Repeated occasions with fojo
Fojo means a distinct occasion. As an ordinary count noun, it takes plural and case endings:
Mi telefonis al la hotelo tri fojojn, sed neniu respondis.
I called the hotel three times, but no one answered.
Ni jam vizitis tiun muzeon du fojojn.
We have already visited that museum twice.
The accusative fojojn expresses how many occurrences the action covered. The cardinal remains invariant.
The compact adverb is written as one word:
La buso haltas ĉi tie dufoje tage.
The bus stops here twice a day.
Ĉu mi devas premi la butonon unufoje aŭ dufoje?
Do I have to press the button once or twice?
Du fojojn and dufoje often describe the same frequency. The first visibly presents a measured count; the second packages that count as an adverb. Both are neutral in conversation and writing.
An adjective in -foja describes something characterized by that number of occurrences:
Post dufoja prokrasto, la koncerto finfine komenciĝis.
After being postponed twice, the concert finally began.
The postponement happened on two occasions. Compare that with duobla prokrasto, which would suggest a doubled amount or a two-part structure rather than simply two events.
The essential contrast: duobla versus dufoja
The difference becomes clearest with the same noun:
La dungito ricevis duoblan pagon por unu longa deĵoro.
The employee received double pay for one long shift.
La dungito ricevis la pagon dufoje: unu parton lunde kaj la reston vendrede.
The employee received the payment on two occasions: one part on Monday and the rest on Friday.
The first concerns amount; the second concerns occasions. In real usage, context sometimes allows fojo in a multiplicative comparison—cent fojojn pli rapide is well attested—but the pedagogically clear default is centoble pli rapide for a factor and cent fojojn for a hundred occurrences.
La fotilo registris la saman eraron kvin fojojn.
The camera recorded the same error five times.
La nova fotilo registras bildojn kvinoble pli rapide.
The new camera records images five times faster.
The first counts error events. The second compares rates.
Comparison patterns with -oble
For an exact ratio, duoble tiel ... kiel ... explicitly sets two equal-looking scales with a factor:
La granda salono estas duoble tiel longa kiel la malgranda.
The large hall is twice as long as the small one.
The common pattern duoble pli longa ol also occurs and is normally understood as “twice as long as”:
La nova itinero estas duoble pli longa ol la rekta vojo.
The new route is twice as long as the direct route.
Because national languages interpret phrases like “two times more” differently, duoble tiel longa kiel or la longo estas la duoblo de... is the clearest wording in contracts, specifications, and (academic) quantitative prose.
For a lower factor, use a fraction or comparison rather than trying to negate -obl-: duone tiel granda, la duono de la antaŭa kvanto, or duoble malpli where context makes the intended inverse relationship clear. Exact technical prose should prefer the explicit fraction.
Multiplication in arithmetic
The adverb form can read a multiplication expression:
Kvinoble sep estas tridek kvin.
Five times seven is thirty-five.
— Kiomoble kvar estas dudek? — Kvinoble.
— Four multiplied by what is twenty? — By five.
Kiomoble? asks for the factor. In mathematical (academic) language, multipliki kvin per sep and kvin multiplikite per sep are also explicit. The -oble pattern is concise and belongs to the same productive system as everyday duoble.
Spelling larger multipliers
The complete numeral is joined to -obl-. Simple compounds are closed: dekduobla “twelvefold,” dudekobla “twentyfold.” Hyphens can preserve boundaries in a longer form: cent-dek-du-obla “112-fold.”
This creates an important written contrast:
La laboratorio mendis dudek duoblajn filtrilojn.
The laboratory ordered twenty double filters.
La laboratorio bezonus dudekduoblan kapaciton por tiu projekto.
The laboratory would need twenty-two-fold capacity for that project.
In the first, dudek counts filters and duoblajn describes each one. In the second, dudekduoblan is a single derived adjective based on 22. Use hyphens when a long multiplier would otherwise be difficult to decode.
Frequency per time unit
Combine an occurrence count with a time expression:
Mi kontrolas la retpoŝton dufoje matene kaj unufoje posttagmeze.
I check email twice in the morning and once in the afternoon.
La kuracisto rekomendis preni la medikamenton tri fojojn tage.
The doctor recommended taking the medicine three times a day.
The time unit commonly appears adverbially as tage, semajne, or jare. Tri fojojn tage counts three occasions within each day. For distribution among people or objects, Esperanto uses po, a different relation addressed on the duration and frequency page.
Common Mistakes
Using -obl- for separate occasions
❌ Mi provis ensaluti trioble hieraŭ.
Incorrect for three separate attempts — trioble expresses a multiplication factor.
✅ Mi provis ensaluti tri fojojn hieraŭ.
I tried to log in three times yesterday.
Using fojo for a doubled amount
❌ Ili pagis al ŝi dufojan salajron ĉi-monate.
Wrong if the salary amount, rather than the number of payments, was doubled.
✅ Ili pagis al ŝi duoblan salajron ĉi-monate.
They paid her double salary this month.
Leaving fojo singular after a larger cardinal
❌ Mi relegis la mesaĝon tri fojo.
Incorrect — fojo is an ordinary count noun and must be plural here.
✅ Mi relegis la mesaĝon tri fojojn.
I reread the message three times.
Separating a multiplier compound
❌ La nova servilo havas dek du oblan kapaciton.
Incorrect spacing for a twelvefold capacity.
✅ La nova servilo havas dekduoblan kapaciton.
The new server has twelvefold capacity.
Confusing repetition with grouping
❌ La gastoj eniris dufoje.
Wrong if the guests entered together in pairs; this says they entered on two occasions.
✅ La gastoj eniris duope.
The guests entered in pairs.
Key Takeaways
Use -obl- for a multiplication factor: duobla, duoble, duoblo. Use fojo, dufoje, and dufoja for separate occurrences. Keep the whole number together before -obl-, retain ordinary plural and accusative endings on fojojn, and use -op-, not either of these patterns, when the meaning is “in groups of.”
Related Topics
- Cardinal NumbersA1 — Use Esperanto cardinal numbers to count, quantify noun phrases, identify items, and read basic dates, times, measurements, and decimal notation.
- Duration and FrequencyA2 — Express how long and how often events occur with measured accusatives, dum-phrases, recurring time expressions, and fojo-based forms.
- Collective and Group NumbersB1 — Describe groups of a stated size with -op-, distinguishing group structure from simple quantity, distribution, and multiplication.
- Numbers as Nouns, Adjectives, and AdverbsB2 — Change Esperanto number words into nouns, adjectives, and adverbs while preserving the distinction between quantity, order, and manner.
- -obl-: Multiplicative QuantityB1 — Use -obl- for multiplication factors and multiple structure, while separating magnitude from repeated occasions, group size, and fractions.
- -ad-: Duration, Repetition, Or Ongoing ActivityB1 — Use -ad- to foreground an action as prolonged, repeated, habitual, or an ongoing process rather than a single event or result.