Definition

1. Noun:
   • A year in the Gregorian calendar containing an extra day (February 29th) to synchronize the calendar year with the solar or astronomical year. It is specifically any year divisible by 4, except for end-of-century years (years divisible by 100), which must also be divisible by 400 to be an intercalary year.

Usage

• The term "intercalary year" is a formal, technical synonym for the more common term "leap year." It is used in scientific, historical, and calendrical contexts.
• It functions as a countable noun.

Examples

• Noun:
  • The next intercalary year will be 2028.
  • The rule for determining an intercalary year was established by the Gregorian calendar reform.
  • Because 2100 is divisible by 100 but not by 400, it will not be an intercalary year.

Advanced Usage

• "intercalary": The adjective form describes the inserted day or period itself.
  • February 29 is the intercalary day.

Variants and Related Words

• Leap year (n): The common, everyday term for an intercalary year.
• Bissextile year (n): An older, historical term with the same meaning, stemming from the Roman practice of doubling the sixth day before the Calends of March.

Synonyms

• Leap year
• Bissextile year (archaic)

Notes on Different Meanings

• The term is specific to calendar systems. While other calendars (e.g., lunisolar) may have intercalary months, the phrase "intercalary year" in modern English almost exclusively refers to the Gregorian calendar's leap year cycle.

Noun

1. in the Gregorian calendar: any year divisible by 4 except centenary years divisible by 400