Decimal and digit grouping

What it is

A written number settles two questions before it states a quantity: which mark divides the whole part from the fractional part, and whether the whole part is broken into groups and by what. A reader who applies the wrong convention reads a different quantity rather than an awkward one.

The space of options is small and fully occupied. The decimal mark is the full stop, U+002E, or the comma, U+002C. The group separator is one of those two, the space, U+0020, its unbreakable counterpart, U+00A0, or nothing. The choices are not independent: a community that groups with the full stop cannot also use it as the decimal mark, so each convention comes as a pair.

This record and the four beside it name a character that is the subject of a rule in words and by its Unicode number rather than showing it as an example of itself. A string quoted from an instrument or a guide keeps its printed form.

Where the expectation comes from

Two authorities of general application govern this class, and they contradict each other about the same string of digits.

• The SI Brochure, ninth edition, provides at 5.4.4 that the decimal marker "shall be either the point on the line or the comma on the line", and that numbers may be divided into groups of three with neither dots nor commas between the groups. Its worked example sets the groups off by spaces and rejects the comma-separated form in terms.
• Türk Dil Kurumu's Yazım Kuralları rule the opposite for Turkish. Numbers of four or more digits are counted from the right in threes and "aralarına nokta konur", the full stop standing between the groups; and "Sayılarda kesirler virgülle ayrılır", the comma separating the fraction. The Turkish code makes the choice the brochure leaves open and, in the same rule, does what the brochure forbids.

The conflict is therefore about which code governs and not whether one does, and it resolves by subject rather than by rank: a community's code governs an ordinary number addressed to that community, and the measurement authority governs measurement matter. That reading is this record's own and is not a rule anyone has published.

The guides narrow without resolving. The English Style Guide separates thousands by a hard space at 6.5, allowing the comma only in graphics, promotional material, press releases and web writing, and at 6.1 requires figures for any number carrying a decimal point "(or a decimal comma in the Official Journal)". The Stijlgids Nederlands of the same Directorate-General blocks by threes from the right separated by a space and separates decimals by a comma, except that "in webteksten worden deze blokken van drie cijfers echter door een punt van elkaar gescheiden". One institution, two language departments, and inside one of them the medium changing the rule.

The Amtliches Regelwerk does not reach digits at all, so German grouping falls to a standards body this section has not opened. The gap is named here and the instrument that fills it is not.

Consequences for translation

The conversion is determinate once the governing authority is known, and identifying that authority is the work.

• Naming the target language does not fix the form. A Dutch measurement report and a Dutch web page take different group separators on one institution's guidance, so a finding that names a language and not an authority cannot be acted on.
• The failure mode is silent. A wrongly converted separator produces a well-formed number of the wrong magnitude, which no reviser reading for sense will catch. It is mechanically checkable and worth checking mechanically.
• Numbers that identify are not touched. An act number or an article number is never grouped and never repunctuated, however many digits it carries, because those digits designate rather than express a quantity.
• A deviation is an error to a competent reader rather than a preference, but the reader in question is that text's: one string can be correct Turkish and incorrect measurement notation at once.

Examples

EN>NL

• Source: Regulation (EU) No 1024/2012
• Target: Verordening (EU) nr. 1024/2012
• Comment: The amending reference in the title of Regulation (EU) 2016/1191, English and Dutch official versions. Four digits, grouped in neither version, although every authority above would group a quantity of that size. The label is converted and the number is carried across untouched, which is the difference between designating and denoting.

EN>TR

• Source: 15 000
• Target: 15.000
• Comment: The English Style Guide's own illustration at 6.5, set off by a hard space. The Turkish target is derived from the code's rule sentence, which puts the full stop between the groups, and not copied from the code's printed examples, which did not survive retrieval intact. Carrying the source form across leaves a Turkish reader a number the code does not recognize.

References

• English Style Guide. Directorate-General for Translation, European Commission, eighth edition January 2016, file consulted 3 August 2026. Chapter 6 (Numbers), beginning at page 38, sections 6.1 (Writing out numbers) and 6.5 (Grouping of thousands).
• Türk Dil Kurumu, Yazım Kuralları, the page Sayıların Yazılışı, read on the institution's own page at tdk.gov.tr. The rules on numbers of four or more digits and on fractions, cited here by their wording; the page's printed examples are not reproduced, the decimal commas in them having been altered in retrieval.
• SI Brochure, The International System of Units (SI), Bureau International des Poids et Mesures, ninth edition 2019, version 4.01 of June 2026, official English text. Section 5.4.4 (Formatting numbers, and the decimal marker), carrying the decision of the 22nd General Conference on Weights and Measures.
• Stijlgids Nederlands. Directoraat-generaal Vertaling, Europese Commissie, vijfde uitgave mei 2025, last amended 21 October 2025. Section 2.2.2.
• Regulation (EU) 2016/1191 of the European Parliament and of the Council of 6 July 2016 on promoting the free movement of citizens by simplifying the requirements for presenting certain public documents in the European Union and amending Regulation (EU) No 1024/2012, English and Dutch language versions, title.