Definition of "Year" :

noun: a body of students who graduate together

"She was in my year at Hoehandle High."

noun: the period of time that it takes for a planet (as, e.g., Earth or Mars) to make a complete revolution around the sun

"A Martian year takes 687 of our days."

noun: a period of time containing 365 (or 366) days

"She is 4 years old."

noun: a period of time occupying a regular part of a calendar year that is used for some particular activity

"A school year."