Semantic Typography

Number & Unit Spacing

A number and its measurement unit normally form one semantic pair and should use the locale’s expected spacing without breaking across lines.

Reviewed 2026-08-20Strong semantic convention with locale exceptionsContext required
CategorySemantic Typography
Rule strengthStrong semantic convention with locale exceptions
Locale applicabilityall
Avellio detectionSupported
Issue identifiersUNIT_SPACE
Correction authorityAn exact recognized pair that passes context guards can enter Safe Clean.

Definition

Spacing distinguishes a value from a glued identifier and prevents the unit from being stranded. Symbols such as degrees, percent, primes, and currencies follow conventions that can differ by locale and discipline.

BAD vs GOOD

BAD
Breakable unit

The sample weighs 12 kg, with kg free to wrap.

GOOD
Protected unit

The sample weighs 12 kg.

Why it matters

A broken number–unit pair is harder to scan and can create ambiguity in technical and tabular material.

Rule strength

Strong semantic convention with locale exceptions. This is not an absolute linguistic law; locale, genre, content, and house style can change the correct decision.

Exceptions and editorial considerations

  • Angular degrees, primes, mathematical notation, identifiers, and specialist standards can use different spacing.
  • Single-letter units require stronger context guards.

How to fix it manually

  1. Confirm the discipline and locale.
  2. Insert the correct NBSP or NNBSP between value and unit.
  3. Keep unit typography consistent across prose, tables, and captions.

Adobe InDesign guidance

Use a non-breaking space character or a narrowly scoped GREP style; do not use No Break across an unnecessarily large range.

How Avellio detects it

Avellio emits UNIT_SPACE for recognized measurement and production units, with additional guards for single-letter tokens.

Action safety

An exact recognized pair that passes context guards can enter Safe Clean.

Check this automatically in Adobe InDesign

Language and locale differences

EN USEN UKEN AUEN NZ

A space is normal for many spelled or SI-like units; English-family Avellio profiles normally do not require a space before %.

FRDECZPLPTBR

Continental profiles commonly expect protected spacing before units and percent, subject to the publication standard.

Compare all published language and locale guides.

Authoritative references

  1. BIPM — SI Brochure, writing quantity values and unit symbolsInternational measurement standard
  2. Avellio User Manual — Locale profile referenceAvellio product source
  3. Avellio User Manual — The Action LayerAvellio product source
  4. Unicode Standard Annex #14 — Unicode Line Breaking AlgorithmUnicode standard

Avellio references document product behavior. External standards and authorities support the general or locale-specific typographic guidance. Where traditions disagree, this page states the disagreement instead of manufacturing one universal rule.