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"Decimal point or decimal sign?
One of the confusions between English and many other European languages is that English uses a decimal point, or dot, on the line to mark the numerator: (6.456). Norwegian and many other European languages use a comma: (6,456). ISO's Council has now ruled on this, which settles the matter as far as ISO documents are concerned:
In documents in the English language, a dot is often used instead of a comma. If a dot is used, it should be on the line. In accordance with an ISO Council decision, the decimal sign is a comma in all ISO documents. ISO 31-0:1992 (E), Note 17. (My stress)
On the other hand, most leading English dictionaries such as the Oxford English Dictionary or Webster's, like the calculator on your desk, make it clear that in other British and American English contexts, the decimal point is the normal decimal marker in English. This is of course why the dot is called the decimal point in these dictionaries, rather than decimal sign.
You are likely to confuse your readers if you are tempted to adopt the ISO standard for non-ISO documents in English. It would be reasonable to guess that 90% of native English readers have never heard of the Council decision in ISO 31-0 and using a comma as a decimal marker in English is probably going to be interpreted as a thousand marker. If you are quoting a unit price of NOK 6,456 per kilo, this may not result in an order as most English or American contractors will probably understand this as: six thousand four hundred and fifty six kroner a kilo.
Thousand marker
ISO 31-0 also considers the confusion of a price in an English document written with a thousand marker as it sometimes is in Norwegian. For example, NOK 145.650. Does this mean NOK 145 or NOK 145 650? (An English law court would probably decide that the price is NOK 145, so be careful, this could be a very expensive mistake.) ISO 31-0 states that such groups of digits are to be separated by a space, never by comma or point (ISO 31-0, Part 3).
A space is also used in English and Norwegian as a thousand marker. However, as I just mentioned with the price of NOK 6,456 it is also common in English to use commas to mark thousands."
