year 
(yîr)
(yîr)n.
1. Any of various calendrical units based on the time the earth takes to revolve once around the sun, especially:
a. In the Gregorian calendar, a period beginning on January 1 and ending on December 31, consisting of 365 or 366 days in 12 months. Also called calendar year.
b. A period of 365 or 366 days used as the basis for another calendar such as the Julian calendar.
c. A period of 12 or 13 lunar months in a lunisolar calendar such as the Jewish calendar.
d. A period of 12 lunar months in a lunar calendar such as the Islamic calendar.
2. A sidereal year.
3. A solar year.
4. A period of about a year: We were married a year ago.
5. A period equal to the calendar year but beginning on a different date: a tax-reckoning year; a farming year.
6. An annually recurring period devoted to a special activity: the academic year.
7. years Age, especially old age: I'm feeling my years.
8. years An indefinitely long period of time: it's been years since we saw her.
[Middle English yere, from Old English gēar; see yēr- in the Appendix of Indo-European roots.]