Definitions of year:

• 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

  Example: "A Martian year takes 687 of our days"

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

  Example: "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

  Example: "A school year"

• noun:   a body of students who graduate together

  Example: "She was in my year at Hoehandle High"