The noun has 4 meanings:
Meaning #1:
a period of time containing 365 (or 366) days
Synonyms: twelvemonth, yr
Meaning #2:
a period of time occupying a regular part of a calendar year that is used for some particular activity
Meaning #3:
the period of time that it takes for a planet (as, e.g., Earth or Mars) to make a complete revolution around the sun
Meaning #4:
a body of students who graduate together
Synonym: class




