The radix point is the decimal separator character.

A third of the world uses a ,, another third use a . and the remaining do not seem to care... And then you have cases like Switzerland which use , for most numbers, and . when talking about money!

In all this we're trying to unify the input so want to something like

Please enter all numbers using a "." as the decimal separator

There will be non-technical people using this, and there will be people from around the world who are used to using , for their decimal separator.

a) Is there a better term for "decimal separator"?

b) Is there a better way to phrase the statement to make it clear what we're asking?

  • 2
    The term 'radix point' is the hypernym for all separators used to show where the whole number part of a number ends. Thus in 101.11 [base 2], = 5.75 as a decimal, the bicimal point is still a radix point. The base ten separator is known generally as a 'decimal separator' or 'decimal mark' (see Wikipedia); 'decimal point' is the most common term at least in the UK, but here commas are not used as separators. // You seem to be asking about a term readily understandable worldwide, but ELU only deals with English language usages. Perhaps Maths SE would be a better place to ask. – Edwin Ashworth Jul 15 '17 at 6:31
  • I'm voting to close this question as off-topic because it belongs on math.stackexchange.com – user66974 Jul 15 '17 at 6:34
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    FWIW, "decimal separator" is clear to me as a native AmE speaker—but then, as a native AmE speaker it probably wouldn't occur to me to use anything other than a ".". You could consider including an example if that fits into the parameters of your project. – 1006a Jul 15 '17 at 6:34
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    @Josh I respectfully disagree, the question isn't about the "radix point" or any mathematic notations, but how to communicate to "a man in the street" what I mean then I say "decimal separator". i.e. how do I communicate the character which goes between the dollars and cents / pounds and pence / euros and cents? Otherwise you'll be saying that "Should I say aircraft, airplane, or aeroplane?" belongs on aviation! – RemarkLima Jul 15 '17 at 6:59
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    @Josh DEFINITELY not about math. Perhaps UX SE instead. RemarkLima, perhaps display the radix but only allow users to type digits? Relying on people following an instruction like that is only kicking the ball down the road. – Spencer Jul 29 '17 at 11:55

Based also on your further comments I interpret your question as primarily "how to specify the decimal separator so all users clearly understand", my answer is rather practical than linguistic :)

Is there a better term for "decimal separator"?

I don't think so.

Is there a better way to phrase the statement to make it clear what we're asking?

Sure, here you have so many possibilities! It depends on the meaning of the number. You may also include a few examples to make it really clear.


  • Enter your height in meters, use "." as decimal separator, e.g. 1m 72cm as "1.72"
  • Enter the price you request, use "." as decimal separator, e.g. 15€ 50cents as "15.50"
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  • 1
    +1 for "decimal separator" being the best term. Ngrams show it's far more common than decimal comma, decimal mark or decimal period, though unsurprisingly dwarfed by decimal point. – AndyT Aug 1 '17 at 10:06
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    Good use of examples, and thank you for inferring that the question is about being understood - the whole point of languages right! – RemarkLima Aug 2 '17 at 7:04

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