perennial

continual, continuous, constant, incessant, perpetual, perennial mean characterized by continued occurrence or recurrence. continual often implies a close prolonged succession or recurrence <continual showers the whole weekend>. continuous usually implies an uninterrupted flow or spatial extension <football's oldest continuous rivalry>. constant implies uniform or persistent occurrence or recurrence <lived in constant pain>. incessant implies ceaseless or uninterrupted activity <annoyed by the incessant quarreling>. perpetual suggests unfailing repetition or lasting duration <a land of perpetual snowfall>. perennial implies enduring existence often through constant renewal <a perennial source of controversy>.

The Latin word annus, meaning “year,” gives us the root ann or enn. Words from the Latin annus have something to do with a year. Anything that is annual happens once a year and anything biennial happens once every two years. An anniversary is the return every year of the date on which something special happened. Something perennial continues all year long or comes back each year.