An academic year is the annual period during which a student attends an educational institution.
The academic year may be divided into academic terms, such as semesters or quarters.
The Greek word for "year", "yearling (calf)", the latter also reflected in Latin vitulus "bull calf", English wether "ram" (Old English weðer, Gothic wiþrus "lamb").
In some languages, it is common to count years by referencing to one season, as in "summers", or "winters", or "harvests".
In English, the abbreviations "y" and "yr" are commonly used.
In astronomy, the Julian year is a unit of time; it is defined as 365.25 days of exactly The word "year" is also used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year, the academic year, etc.
As 218 out of every 900 years are leap years, the average (mean) length of this Julian year is A calendar era assigns a cardinal number to each sequential year, using a reference point in the past as the beginning of the era.
Worldwide, the most commonly used calendar era is referenced from the traditional—now believed incorrect—year of the birth of Jesus.
The ISO standard ISO 80000-3, Annex C, supports the symbol "a" (for Latin annus) to represent a year of either 365 or 366 days.
Similarly, "year" can mean the orbital period of any planet: for example, a Martian year or a Venusian year are examples of the time a planet takes to transit one complete orbit.
The term can also be used in reference to any long period or cycle, such as the Great Year.
In temperate and subpolar regions around the globe, four seasons are generally recognized: spring, summer, autumn and winter.
In tropical and subtropical regions several geographical sectors do not present defined seasons; but in the seasonal tropics, the annual wet and dry seasons are recognized and tracked.