i18n Key Naming for Pluralization Rules

Naming i18n Keys for Pluralization

Pluralization is one of the most complex aspects of i18n because languages have vastly different plural rules. English has two forms (singular and plural), but Arabic has six, Russian has three, and Japanese has none.

CLDR Plural Categories

The Unicode CLDR (Common Locale Data Repository) defines six plural categories:

Category	English Example	Used By
zero	0 items	Arabic, Latvian, Welsh
one	1 item	Most languages
two	2 items	Arabic, Hebrew, Slovenian
few	3 items	Czech, Polish, Russian
many	5 items	Arabic, Polish, Russian
other	10 items	All languages (required)

Key Patterns by Library

react-i18next / i18next

{
  "items_count_one": "{{count}} item",
  "items_count_other": "{{count}} items",
  "items_count_zero": "No items"
}

Or with nested structure:

{
  "items": {
    "count_one": "{{count}} item",
    "count_other": "{{count}} items"
  }
}

vue-i18n

{
  "items_count": "No items | {{count}} item | {{count}} items"
}

Vue-i18n uses pipe-separated values within a single key.

ICU MessageFormat

{
  "items_count": "{count, plural, =0 {No items} one {# item} other {# items}}"
}

ICU MessageFormat is the most powerful and language-aware approach, used by next-intl, FormatJS, and Angular.

Rails I18n

en:
  items:
    count:
      zero: "No items"
      one: "%{count} item"
      other: "%{count} items"

Best Practices for Plural Keys

1. Always include the other form -- it is the required fallback in all languages
2. Never hardcode numbers -- use {{count}} interpolation, not separate keys for each number
3. Include zero when the empty state has special text -- "No items" vs "0 items"
4. Test with languages that have complex plural rules -- Arabic, Polish, and Russian catch edge cases
5. Use ICU MessageFormat for new projects -- it handles all plural categories and nested selects

Ordinal Plurals

Some languages have ordinal forms (1st, 2nd, 3rd):

{
  "place": "{count, selectordinal, one {#st} two {#nd} few {#rd} other {#th}}"
}

This is only available with ICU MessageFormat.