One of the answers I occasionally write at LinkedIn Answers seemed worth reposting here. The question was: “Do all languages in the world use Western numerals (1, 2, 3 etc) to express numerical values?“. My answer (slightly revised):

The simple answer to your question is, “No”. Or, “Yes”. It depends which exact question you are asking.

Is it the case that all languages in the world use only Western numerals (usually known as “Arabic” or “Hindu-Arabic numerals“, by the way) to express numerical values? No. Many languages use multiple number forms, depending on context. In the English language, for example, a numerical value could be expressed with words (”one”) in text, Hindu-Arabic numerals (”1″) in a technical context, or Roman numerals (”i”, “I”) in lists. Arabic, Hindi, Japanese, and Chinese all have native characters to express numerical values, which are used in some contexts.

Do all languages in the world use Western numerals sometimes, in some contexts, to express numerical values? Yes — mostly, probably. The qualifications are because I hate to make generalisations about human culture; it’s so diverse. And, note that languages without written forms probably don’t use Hindu-Arabic numerals at all.

Is it the case that Western numerals are — in all cultures, in all contexts — the idiomatic, preferred way to express numerical values? No. They aren’t even sufficient for all contexts in English (viz “one”, “i”).

Do all cultures which use Western numerals to express numerical values do so in the same way? No. In particular, the punctuation between the whole and the fractional part of a number, and the grouping of digits, differ by cultures. North America uses “1,234,567.89″; many European cultures use “1.234.567,89″; I’ve seen Japanese texts that say “123,4567.89″. See the CLDR number format patterns, creating international number formats in Excel, and the user guide to ICU formatting numbers.

Let’s shift focus from expressing numbers in cultures to implementing numbers in software products.

If you were making priority decisions for a software product (that’s my background) to expand its market internationally, and that product expresses numerical values using Hindu-Arabic numerals in some contexts appropriate in North America, can you be confident that it’s the only system you’ll need to express numerical values? No. You of course need to look at the cultural requirements of each new market as you go. But I’m confident that over time, some market will require some system other than Hindu-Arabic numerals to express numerical values. So I’m confident that sooner or later, you will have to give that software product the ability to express numerical values in a variety of ways (i.e., to internationalise it).

Postscript: the questioner, LinkedIn product manager Minna King, was kind enough to mark this as the “Best Answer” of the six posted.

[Edited for clarity based on reader feedback.]