noun A period of time akin to the time taken for the Earth to undergo a full cycle of seasons.
we moved to this town a year ago; I quit smoking exactly one year ago
noun The time taken for the Earth to return to the same position along the ecliptic, completing a full cycle of seasons; a tropical year or solar year.
noun The time taken for the Earth to orbit the Sun with respect to the fixed stars; a sidereal year.
noun The length of twelve lunations; the time taken for any moon phase to happen twelve times; a lunar year.
noun The length of a year as marked by a calendar, 365 or 366 days in the Gregorian calendar; a calendar year.
noun The mean length of a calendar year in the Julian calendar, that is, 365.25 solar days; a Julian year.
noun An orbital period: the period of one revolution in any particular orbit: The time it takes for any astronomical object (such as a planet, dwarf planet, small Solar System body, or comet) in direct orbit around a star (such as the Sun) to make one revolution around the star.
Mars goes around the sun once in a Martian year, or 1.88 Earth years.
noun A period between set dates that mark a year, such as from January 1 to December 31 by the Gregorian calendar, from Tishri 1 to Elul 29 by the Jewish calendar, and from Muharram 1 to Dhu al-Hijjah 29 or 30 by the Islamic calendar.
A normal year has 365 full days, but there are 366 days in a leap year.