What it is
A measured quantity is written as a figure followed by a symbol, and the only question the pair raises is what stands between them: a space, U+0020, its unbreakable counterpart, U+00A0, or nothing. The same question is put by a group of signs that behave like units without necessarily being units, the percent sign, U+0025, the per mille sign, U+2030, the degree sign, U+00B0, and the prime and double prime, U+2032 and U+2033.
The choice looks trivial and is not, because it is made three times over: whether there is a space at all, whether it may break across a line, and, for some signs, which side of the figure the sign stands on. No language system settles any of the three.
A unit symbol is an abbreviation that never takes a full stop, and whether an abbreviation takes one is abbreviation-and-ordinal-punctuation. This record owns the space rather than the point.
Where the expectation comes from
The line between the tiers runs inside this record rather than around it.
- The SI Brochure, ninth edition, is the anchor. At 5.4.3 "The numerical value always precedes the unit and a space is always used to separate the unit from the number", and its worked examples make the rule visible in both directions, a Celsius temperature written with the space and the closed-up form rejected beside it. The same section closes up the symbols for degree, minute and second of plane angle, which its own worked example prints without spaces. That is an international standard of general application, binding on anyone writing measurement matter.
- On the percent sign four authorities give three answers and the brochure gives none that could be verified here. The English Style Guide closes the sign up to the figure. The Stijlgids Nederlands requires a fixed space before it, "Dit wordt voorafgegaan door een vaste spatie", except in web texts, where it requires none. Türk Dil Kurumu's Yazım Kuralları leave no space between the numeral and the percent or per mille sign, "Yüzde ve binde işaretleri yazılırken sayılarla işaret arasında boşluk bırakılmaz", and the code's examples place the sign before the numeral rather than after it. The Office québécois de la langue française requires an unbreakable space before it.
- Whether the brochure treats the percent sign as a unit at all was not established, so no classification of that sign is attributed to it here.
So the presence of a space between a value and a unit symbol is Codified, and so is the closing up of the plane-angle symbols, the one place in this record where an absent space is the rule rather than an error. The percent sign sits on both sides of the line at once, House in English and Dutch and Codified in Turkish. Unbreakability is a separate matter again: the brochure requires a space without requiring that it be unbreakable, the two institutional guides add that requirement, and the Quebec rule imposes it as a language authority. No measurement authority opened here demands it.
Consequences for translation
The value is Codified and the rule a translator meets most often is not, which makes naming the authority more useful here than naming the tier.
- Closing up a unit symbol is a finding any competent reader of measurement matter would flag. Closing up the percent sign obeys the English guide and breaches nothing that has been shown to rule it, and neither statement is a preference.
- The unbreakable space is a typographic requirement, not an orthographic one. It is invisible in a rendered line and detectable in the file, so it is exactly the class of compliance worth checking mechanically and impossible to check by reading.
- The symbol itself is carried across untouched. What converts is the spacing and the position, so the retention question this family raises elsewhere is real here and very thin.
- A reviser who normalizes every symbol to a spaced form breaks the plane-angle rule, and one who normalizes every sign to a closed-up form breaks the unit rule. Neither sweep is safe.
Examples
EN>NL
- Source: 30.2 °C
- Target: 30,2 °C
- Comment: The brochure's own illustration at 5.4.3, which prints the closed-up form beside it as wrong. The space survives the language pair untouched because a measurement authority rules it, while the decimal mark converts under the neighbouring record. One short expression, two conventions, and only one of them moves.
EN>FR
- Source: 25%
- Target: 25 %
- Comment: The English guide's own illustration, the sign closed up to the figure. The French target follows article 22039, which requires an unbreakable space before the sign. The conversion is not from a wrong form to a right one: each is correct where it was written, and a translator who carries the source form across has obeyed one authority in the other's territory.
References
- English Style Guide. Directorate-General for Translation, European Commission, eighth edition January 2016, file consulted 3 August 2026. Chapter 6 (Numbers) for the percentage rule, cited by chapter because the retrieval route returned conflicting section numbers for it, and section 6.1 for units with figures.
- 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 5.4.3 (Formatting the value of a quantity).
- Türk Dil Kurumu, Yazım Kuralları, the page Sayıların Yazılışı, read on the institution's own page at tdk.gov.tr. The rule on the percent and per mille signs, cited by its wording; the page's printed examples are not reproduced, and the position of the sign is reported from them rather than from the rule, which governs the space alone.
- Banque de dépannage linguistique, "Espacement avant et après les signes de ponctuation et les symboles", article 22039, Office québécois de la langue française, last updated 2024.
- Stijlgids Nederlands. Directoraat-generaal Vertaling, Europese Commissie, vijfde uitgave mei 2025, last amended 21 October 2025. The section on symbols and units of measurement, cited by edition; the retrieval route returned no section number for it that could be relied on.