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Number Words


Number Words will build numeric expressions for natural numbers, percentages and fractions. For example:

  • 0.231 will be converted to less than a quarter,
  • 102 to over one hundred.

Supports multiple languages.

The implementation is based on ideas expressed in Generating Numerical Approximations.

Numerical Approximations

Numerical approximations are all over texts based on data:

- Water temperature is below 10C (input data would be 9.53C)
- A third of students failed the exam (34.3%)
- Q2 sales were over 1M$ (1,002,184 $)

Numeric data providing information about some metrics of interest is often a number with the precision we do not need. If we see 9.382%, the information we need is likely - almost 10% - instead of the precise number. Furthermore, different approximation strategies are often used in the report involving the same metrics. At the beginning of the report we might say almost 10% or "below 10%" while later in the text, we might choose a more precise expression - around 9.4%.

Number Words will help you build such numerical approximations. Making them available for the text generation systems.


Number Words uses the following abstractions:

  • Actual Value is a number which needs to be approximated - an input to the approximation function. In the examples above it is the temperature - 9.53C, or the percentage 34.3%.
  • Scale of approximation. It is a snapping grid across the range of numbers along which the approximation is done. The scale to use is determined by the domain. For example:
    • 1/4 scale, will form approximation steps starting at 0 then 1/4, 1/2, 3/4 ending with 1;
    • 1/10 scale will express percentages with one precision point;
    • scales which are multiples of 10 are useful for natural number approximation. The 10 will round to tens: 1007 -> 1010, the 100 to hundreds: 1003 -> 1000, and so on.

The result of actual value approximation to a given scale provides:

  • Given Value a discrete value along the scaled number range to which actual value is the closest.
  • Hedge a common use word describing the relation between actual and given values. Actual Value of 9.5 is below the given value of 10. Actual Value of 101 is over the given value of 100.
  • Text a textual spell out of the given value. A 2666 is Two thousand six hundred sixty six.
  • Favorite Number expresses some common language names for certain numbers. A 0.25 is a favorite number in that that it has the name - a quarter.

A full approximation result returns three such approximation data structures for a given value which is:

  • less than the actual value on the scaled number range.
  • more than the actual value on the scaled number range.
  • around the actual value on the scaled number range. For this 'less' or 'more' value closer to the actual value is chosen.

Lastly the number formatting can be specified:

  • words - spell out the number in words (110 -> hundred and ten).
  • bites - spell out the number using bite size style shortening (1022 -> 1k).
  • numbers - report number as is.


Numeric approximation has two functionality points which are language dependent

  • Hedges which will differ from language to language. See Configuration section to see how this can be controlled.
  • Text number to text translation for a given value. For this translation Number Words relies on ICU4J.

Currently supported languages:

  • French
  • German
  • English
  • Lithuanian
  • Portuguese
  • Russian


Number Words exposes approximation functionality through numeric-expression function which takes on the following parameters:

  • actual-value - the number to approximate
  • scale - at which the approximation is to be performed.
  • language - use two letter language code (like :pt), default is :en
  • relation - what kind of relation to between actual and given value to use (valid values specified in :numberwords.domain/relation)
  • formatting - which number formatting should be used (valid values specified in :numberwords.domain/formatting)


Number Words is available as a Maven artifact from Clojars.



[ai.tokenmill.numberwords/numberwords "1.1.0"]


ai.tokenmill.numberwords/numberwords {:mvn/version "1.1.0"}

Usage example:

(require '[numberwords.core :as nw])

(numeric-expression 144 10 :en :numberwords.domain/around :numberwords.domain/words)
"around one hundred forty"

(numeric-expression 144 10 :de :numberwords.domain/less :numberwords.domain/numbers)
"weniger als 150"

;; with defaults
(numeric-expression 144 10)
"around 140"


Get a jar by building it with

clojure -A:uberjar

Or as a Maven dependency


Usage example:

import ai.tokenmill.numberwords.NumberWords;

NumberWords nw = new NumberWords();
nw.numericExpression(1.22, 0.1, "en", "more", "numbers");


Hedges, favorite numbers can be modified and new languages added via changes to a configuration file - resources/numwords.edn

{;;Configuration is structured by the language 
 :en {
      ;;Hedges section specifies which words are associated with given actual to given value relations
      :hedges {:equal  #{"exactly"}
               :around #{"around" "approximately" "about"}
               :more   #{"more than" "over"}
               :less   #{"less than" "under" "nearly"}}
      ;;Favourite numbers map a special number with its textual expressions
      :favorite-numbers {1/4  #{"a quarter" "a fourth"}
                         1/2  #{"a half"}}}}


Copyright © 2020 TokenMill UAB.

Distributed under the The Apache License, Version 2.0.

Photo by Amanda Jones on Unsplash

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