Grammar and mechanics

The rule

Sentence case everywhere, no full stop on a label, and a space between a number and its unit. The exceptions are a short, closed list.

This page exists because two components in the roster do nothing but emit formatted strings. Value renders a number with a unit; RelativeTime renders a moment. If the mechanics are not written down, each caller invents them, and a product ends up saying "72bpm" on one screen and "72 BPM" on the next, which looks careless in a context where carelessness reads as unreliability.

The boundary with the clinical rules

This page owns typography: which case, which space, which dash, which separator. It does not own precision.

How many decimal places a value may carry, when a conversion between unit systems is safe, and what rounding is honest are clinical correctness questions and they belong to Numbers, units and precision, which is canonical for them. If this page and that page appear to disagree, that page wins.

Capitalisation

• Sentence case for everything: headings, buttons, labels, menu items, table headers, notification titles, error messages. Title Case is a decorative convention that costs scanning speed and creates two spellings of every string.
• Capitalise proper nouns only, including brand names of medicines and devices. Condition names are not proper nouns: "type 2 diabetes", not "Type 2 Diabetes".
• Preserve the case of clinical terms and units. "HbA1c", "mmHg", "mmol/L", "SpO2". These are not sentence-cased and are not upper-cased for emphasis.
• Two spellings, and they are not interchangeable. The four level ids are steady, watch, attention and urgent, and they are lower case wherever you write about them. The component renders its own sentence-case word beside the colour and the icon: "Steady", "Watch", "Needs attention", "Urgent", plus "Not known" where there is no reading. Never re-case, abbreviate or translate the rendered word; it comes from CLINICAL_STATUS_META in lib/status.ts and it is the thing the colour is not allowed to carry alone.

Punctuation

• No full stop at the end of a label, a button, a heading, a table cell or a single-sentence hint. Full stops in full sentences, including single sentences inside a paragraph.
• No exclamation marks. There is no situation in a health interface improved by one.
• Ampersand only where it is part of a name. "Diet and exercise", not "Diet & exercise".
• Never an em dash and never an en dash. Not in interface copy, not in a heading, not in a code comment, not in a data file. A sentence that seems to want one is carrying two statements, so write the two. Dropping a comma, a colon, a semicolon, a bracket, a hyphen or three dots into the gap is the same sentence still reaching for a dash.
• Use a real minus sign for a negative number. A hyphen in "-2 kg" can be misread. The minus sign is arithmetic notation rather than punctuation, and this rule does not touch it.
• Use a non-breaking space between a number and its unit so a value never wraps across two lines. A reading split as "148" at the end of one line and "mmHg" at the start of the next is a value the reader has to reassemble.
• Serial comma only where it removes ambiguity. Consistency here is worth less than clarity; do not enforce it mechanically.
• Straight quotes and apostrophes in code, typographic ones in prose.

Lists

• Introduce a list with a full sentence ending in a colon.
• Every item starts with a capital and has no terminal punctuation, unless items are full sentences, in which case all of them are.
• Items are grammatically parallel. If one starts with a verb, all do.
• A list of more than seven items is a table or a set of sections. Health content routinely produces long lists of symptoms or medicines, and past about seven a list stops being scannable.

Abbreviations and acronyms

• Expand on first use, in the reader's word order: "blood pressure (BP)", not "BP (blood pressure)". After that the short form is fine within the same screen. It is not fine across screens, because a reader may not have seen the first one.
• Never abbreviate in a notification, an alert or an empty state. These are the surfaces most likely to be somebody's first encounter with the product.
• No full stops in acronyms. "GP", not "G.P."
• Latin abbreviations are banned outright: e.g., i.e., etc., approx. Write "for example", "that is", "and so on", "about".

Numbers and units

• Numerals for all measurements and quantities, including one through nine. "3 readings", not "three readings". Health content is scanned, and numerals scan.
• A space between the number and the unit. Write 148 mmHg, 72 bpm, 5.4 mmol/L and 82 kg. Closed exceptions, which take no space: the degree symbol in 36.8°C, the percent sign in 98%, and the prime marks in angles.
• Unit symbols are never pluralised and never take a full stop. 5 kg, not 5 kgs.
• Digit grouping with a thin space or a comma, consistently, above four digits. Never group a four-digit number that is a step count and never group a year.
• A leading zero on a decimal below one. 0.8 mmol/L, not .8 mmol/L. The missing zero is a genuine misreading risk.
• Write a blood-pressure pair with the word "over" in prose and with a slash only in a compact numeric display: "148 over 92" in a sentence, 148/92 in a table cell.
• Ranges use the word "to", never a dash and never a hyphen. "90 to 120", "90 to 120 mmHg", "3.9 to 5.6 mmol/L". The unit is written once, after the second number. This holds in a table cell and an axis label as well as in a sentence, because a range is two numbers and a relation, and the relation has a word.

Approved / Rejected

Patterns

A value with a unit

number + a non-breaking space + unit symbol

Rendered by Value, which owns the non-breaking space so that no caller has to remember it.

A value with its comparison

value unit + a full stop + Your usual range is low to high unit

The unit appears twice on purpose. A range printed without its unit next to a value that has one is the sort of asymmetry that makes readers doubt both.

A blood pressure

In prose: systolic over diastolic In a compact display: systolic/diastolic

A first-use abbreviation

full phrase in the reader's words (abbreviation)

A list introduction

Full sentence describing what the list is:

A percentage in a non-actionable context

n%

Only where the reader is not being asked to act on it. In an actionable sentence, use a natural frequency instead. See Health literacy.

Banned words

Constructions rather than words, because that is what mechanics are made of.

Related components

• Value owns number-and-unit typography: the non-breaking space, the unit symbol casing, the leading zero and the digit grouping. Every rule in the Numbers section above is a requirement on it.
• RelativeTime owns the choice between a relative phrase and an absolute stamp, and the capitalisation of both. See Numbers, dates and time.
• StatusPill renders one of the four status words, whose casing is fixed here.
• Field follows the capitalisation and punctuation rules above in its labels, hints and error text; a field whose label ends in a colon on one screen and not the next is the most visible mechanics failure in any product.
• Term preserves the case of a clinical term exactly as the reader will meet it.