The official suffix -obl- expresses multiplication by the number before it. Duobla means doubled or twofold, duoble means by a factor of two, and duoblo is a quantity twice as large. The suffix concerns magnitude or multiple structure—not how many times an event occurred.
English twice and three times can express either a factor or repeated occasions. Esperanto normally separates them: duoble pli granda compares size, while dufoje okazis counts two events. All unlabelled forms on this page are neutral contemporary Esperanto.
The base supplies the multiplication factor
-Obl- attaches to numerals and number-like quantity expressions. The numeral says what factor to multiply by; the ending determines how the result functions:
| Form | Word class | Core meaning |
|---|---|---|
| triobla | adjective | threefold; multiplied by three |
| trioble | adverb | by a factor of three |
| trioblo | noun | a quantity three times as large |
La hospitalo proponis duoblan pagon por la feria deĵoro.
The hospital offered double pay for the holiday shift.
La nova kuirilaro funkcias trioble pli longe ol la malnova.
The new battery pack works three times as long as the old one.
Sesdek estas la trioblo de dudek.
Sixty is three times twenty.
In duobla pago, the relevant amount is multiplied by two. The phrase does not say that payment happens on two dates. In trioblo de dudek, the noun trioblo is the semantic head: a threefold quantity of twenty.
Adjectives: multiplied magnitude and multiple structure
An -obl-a adjective most often describes a quantity compared with a reference: duobla prezo, triobla distanco, kvinobla risko. The reference may be stated with de, kompare kun, or a comparison phrase, or it may be understood from context.
Pro la urĝa livero ni pagis preskaŭ duoblan prezon.
Because of the urgent delivery, we paid almost double the price.
Ĉu la pli granda salono vere havas trioblan kapaciton?
Does the larger hall really have triple the capacity?
An -obl-a form can also describe something composed of that many corresponding layers or parts. Duobla fadeno consists of two threads used together; duoblaj fenestroj have a doubled glazing structure; duobla lito is conventionally a bed for two.
La duoblaj fenestroj bone izolas la apartamenton kontraŭ strata bruo.
The double windows insulate the apartment well against street noise.
This structural extension is established, but not every object with two ordinary members takes -obl-. A committee with two members is duopa komisiono, because the relevant relation is group membership. The choice reflects the semantic head: multiple construction versus member group.
Adverbs: factor in comparisons and change
The adverb -oble modifies a property, action, or comparison by a factor. A highly explicit equality comparison uses duoble tiel ... kiel ...:
La ĉefa koridoro estas duoble tiel longa kiel la flanka.
The main corridor is twice as long as the side corridor.
The widespread pattern duoble pli ... ol ... also normally expresses the same factor:
La ĉirkaŭvojo estas duoble pli longa ol la rekta itinero.
The detour 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 pedagogically safest in (formal) contracts, specifications, and (academic) quantitative writing.
The factor can modify a change or rate rather than a static property:
Post la ĝisdatigo la programo startas kvaroble pli rapide.
After the update, the program starts four times faster.
Do not infer four separate start events. The program's starting speed is compared multiplicatively.
Arithmetic and question forms
In arithmetic, -oble can state multiplication directly:
Sesoble ok estas kvardek ok.
Six times eight is forty-eight.
— Kiomoble ses estas kvardek du? — Sepoble.
— Six multiplied by what is forty-two? — By seven.
Kiomoble? asks for the factor. The independent verb obligi means “multiply,” though multipliki is also common and especially transparent in (academic) mathematics. Oblo can stand for a multiple in statements such as dek estas oblo de du.
Number-like words also combine productively: multobla means multiple or manyfold, and multoble means many times as much/by a large factor.
La projekto postulos multoble pli da memoro ol la antaŭa versio.
The project will require many times more memory than the previous version.
-Obl- versus occasions with fojo
This is the essential contrast for English speakers:
La teknikisto ricevis duoblan pagon por unu nokta riparo.
The technician received double pay for one nighttime repair.
La kliento erare pagis la saman fakturon dufoje.
The customer accidentally paid the same invoice twice.
Duobla pago concerns the size of the amount. Dufoje concerns two occasions. An adjective shows the same difference: duobla kontrolo can mean a doubled or two-layer check, while dufoja kontrolo means checking on two separate occasions.
Ni kontrolis la adreson dufoje, sed ne faris duoblan laboron.
We checked the address twice, but we did not do twice the amount of work.
Older and modern texts sometimes use fojojn in factor comparisons, such as cent fojojn pli rapide. That is attested and understandable, not a grammatical impossibility. The recommended learner distinction is nevertheless valuable: use centoble for an exact factor and cent fojojn for a hundred events. It removes an ambiguity that English often leaves unresolved.
-Obl-, -op-, and -on-
The three official numeral suffixes encode different operations:
| Suffix | Operation | Example |
|---|---|---|
| -obl- | multiply by N | triobla pago |
| -op- | group with N members | triopa komisiono |
| -on- | divide into N equal parts | triono de la pago |
La triopa komisiono petis trioblan buĝeton, sed ricevis nur trionon de tiu sumo.
The three-member committee requested triple the budget but received only one third of that amount.
The repeated tri- does three different jobs. Morphological order is transparent: the number comes first and the suffix determines how that number structures the result. See the broader multipliers and repetitions page for numerical use across whole sentences.
Decimal and complex factors
The whole numerical expression belongs before -obl-. Simple forms are closed: dekduobla, dudekobla. Longer forms can use hyphens at the boundaries where the original numeral had spaces: cent-dek-du-obla “112-fold,” du-mil-dudek-oble “by a factor of 2,020.”
Decimals are possible in technical use: 3,14-oble, read tri-komo-unu-kvar-oble. This is chiefly (academic/technical) notation; ordinary prose usually phrases an awkward factor explicitly.
La nova sentilo registras ŝanĝojn 2,5-oble pli rapide ol la malnova.
The new sensor records changes 2.5 times faster than the old one.
One written contrast exposes scope:
La laborejo mendis dek kvin duoblajn vitropanelojn.
The workshop ordered fifteen double glass panels.
La laboratorio bezonus dudekduoblan kapaciton.
The laboratory would need twentyfold capacity.
In the first, dudek counts filters and duoblajn describes each. In the second, dudek is inside a single multiplier adjective. English spacing must not be copied mechanically.
Lexicalization and restraint
Frequent forms such as duobla, triobla, and multobla have broad established uses. New exact factors remain interpretable, but a mathematically possible formation can be stylistically clumsy. In a public-facing text, deksepoble pli granda ol... may be recast as dek sep fojojn tiel granda kiel... when the full comparison makes the factor unmistakable. In technical prose, formulas and explicit ratios are often best.
The choice is communicative, not a limitation of the grammar. Productivity licenses the form; convention and processing difficulty determine whether readers will welcome it.
Common Mistakes
Using -obl- for repeated occasions
❌ Mi kontrolis la seruron trioble hieraŭ.
Incorrect for three separate checks — trioble states a multiplication factor.
✅ Mi kontrolis la seruron tri fojojn hieraŭ.
I checked the lock three times yesterday.
Using foj- for a doubled amount
❌ La firmao pagis al ŝi dufojan salajron en Decembro.
Incorrect if one salary amount was doubled.
✅ La firmao pagis al ŝi duoblan salajron en Decembro.
The company paid her double salary in December.
Confusing group size with multiple structure
❌ La komisiono estas kvinobla.
Incorrect for a committee with five members — this describes multiplicative structure.
✅ La komisiono estas kvinopa.
The committee has five members.
Using multiplication where division is intended
❌ Mi manĝis duoblon de la kuko.
Incorrect for half of the cake — duoblo is twice an amount.
✅ Mi manĝis nur duonon de la kuko.
I ate only half of the cake.
Separating one multiplier word
❌ La servilo bezonas dek du oblan kapaciton.
Incorrect spacing for a twelvefold factor.
✅ La servilo bezonas dekduoblan kapaciton.
The server needs twelvefold capacity.
Key Takeaways
-Obl- makes multiplication the semantic head: -obla describes a multiple, -oble gives a factor, and -oblo names the resulting quantity. Keep it separate from fojo for occasions, -op- for group membership, and -on- for equal fractional parts. Put the whole factor before the suffix, and use explicit comparisons when international readers could interpret “times more” differently.
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Start learning Esperanto →Related Topics
- -op-: Groups Of A Stated NumberB1 — Use -op- to turn a number into a group size, distinguishing members acting together from simple counting, distribution, repetition, and multiplication.
- -on-: Fractional QuantityB2 — Use -on- to divide a whole into a stated number of equal parts, with the denominator inside the word and any larger numerator outside it.
- -foj-: Number Of OccasionsB2 — Use fojo and compact -foj- compounds to count occasions, distinguishing repetition from multiplication, duration, grouping, and ordinal sequence.
- Multipliers and RepetitionsA2 — Distinguish multiplication with -obl- from repeated occasions with fojo, and form each pattern productively.
- Quantity ComparisonB2 — Compare amounts and counts with pli da, pli multaj, tiom… kiom…, and numerical thresholds while keeping degree and addition distinct.
- Decimals, Percentages, and Mathematical ReadingB2 — Read and write decimal commas, percentages, signed numbers, and common arithmetic expressions clearly in Esperanto.