# International style

Following international style helps readers with limited English proficiency. It also helps translators — human or machine — localize writing by minimizing the burdens of cultural and customary language usage.

Basic rules:
- Write in simple structures.
- Don't use idiomatic or colloquial expressions.
- Avoid shortcuts, symbols, and abbreviations that could easily be spelled out.
- Express data using the standard international conventions outlined below. Vary from these standards only when there's a truly compelling advantage in using a proprietary or customary style.

## Countries

Country names are represented by a two-character code per **ISO 3166** (https://www.iso.org).

Use the code in a table, column, or row that clearly indicates it represents a country.

| Code | Country |
|------|---------|
| DE | Germany |
| ES | Spain |
| FR | France |
| IT | Italy |
| JP | Japan |
| MX | Mexico |
| US | United States |

## Currency

Currency amounts are expressed with a three-letter currency code per **ISO 4217**.

**Why codes, not symbols:** Currency codes are specific to a currency and can't be confused or misinterpreted by the reader. Currency symbols such as the dollar sign ($) aren't unique and are easily misread.

**Usage:** Write the amount followed by a space and the currency code in capitals.

> The computer is priced at 1199 USD.
> The computer costs 1980 EUR.

| Code | Currency |
|------|----------|
| CAD | Canadian dollar |
| EUR | euro |
| GBP | pound sterling |
| JPY | yen |
| USD | U.S. dollar |

## Dates and times

Dates are expressed as year, month, day and are separated by a hyphen. Times are expressed on a 24-hour clock. Per **ISO 8601**.

**Rationale:** Date and time formats are represented with the largest units given first. From left to right the ranking is year, month, week, day, hour, minute, second. This standard, in addition to being used in many Asian languages, solves ambiguities in the date notations used in Canada, the United States, and the United Kingdom.

**Usage:** A colon separates hours, minutes, and seconds. Coordinated Universal Time (UTC) times are expressed as "Z." Local time zones are expressed as the number of hours from UTC.

> Apple Watch Series 9 was introduced on 2023-09-12.
> The file will be posted at 18:00Z.
> The file will be posted at 18:00 PST (UTC−8).

## Decimals

Decimals are expressed by a period or comma. For numbers larger than 999, don't use a period or comma as a separator. A nonbreaking space (Option-Space bar) may be used instead. Per **BIPM SI Brochure** (https://www.bipm.org).

**Rationale:** Breaking up large numbers makes them easier to read, especially in tables. A nonbreaking space can't be misinterpreted as a decimal marker.

**Usage:** Use a period to produce a decimal in English. Numbers may be divided in groups of three on either side of the decimal to make them easy to read. Use a nonbreaking space instead of a period or comma to divide numbers. Express large numbers in their smallest form to make them easier to read.

> A kilobyte is 1024 bytes.
> Apple sold 300 000 iMac computers in the first quarter.
> Apple sold 3.7 million iMac computers in 2 years.

## Languages

Language names are represented by a two-character code per **ISO 639**.

| Code | Language |
|------|----------|
| de | German |
| en | English |
| es | Spanish |
| fr | French |
| it | Italian |
| jp | Japanese |
| nl | Dutch |
| mul | Multiple languages |

In some cases, append an extension to the code to represent a particular localization:

| Code | Language |
|------|----------|
| en-GB | British English |
| zh-CN | Simplified Chinese |
| zh-TW | Traditional Chinese |

## Telephone numbers

Telephone numbers begin with the plus sign and are followed by the country code, the city code, and the number. Freephone (toll-free) numbers are expressed in the local style. Always give a toll number if one is available. Per **ITU-T E.123**.

**Rationale:** The plus sign (+) represents any number a caller must dial to get an outside line, like 9. The caller then dials the remaining digits. Freephone numbers are usually impossible to dial globally, even between Canada and the United States. Providing a freephone number with a toll number allows customers to call no matter where they're from.

**Usage:** Breaks in national numbering plans may be represented by a space. Toll-free numbers are expressed in the local style.

> You can reach Apple by calling +1 408 996 1010 or 800-692-7753 (in North America).
> You can reach Apple France by calling +33 1 69 86 34 00 or 0800 046 046.

## Units of measure (international)

Use only units of the International System of Units (SI) to express the values of quantities. Equivalent values in nonmetric units may be given in parentheses following SI values in cases where safety may be an issue, or when they're used in a product's name. Per **BIPM SI Brochure**.

**Usage:** Quantities are always expressed with a unit symbol. Use a nonbreaking space (Option-Space bar) between the quantity and its symbol. Unit symbols are unaltered in the plural, and are never hyphenated, even when used as an adjective. Unit symbols aren't followed by a period unless they appear at the end of a sentence. Don't imply more precision than is reasonable in choosing a unit symbol.

> The Apple HDMI to HDMI Cable is 1.8 m long.
> The 13-inch MacBook Air computer weighs 1.35 kg.
> The iPad mini 4 Wi-Fi models weigh 298.8 g (0.65 lb.).
> The iMac computer has a 1.6 GHz, 2.8 GHz, or 3.1 GHz processor.

See also [units-of-measure.md](units-of-measure.md) for the full SI unit table and U.S. document conventions.
