Common Words:
* Annual: Happening once a year.
* Anniversary: The yearly celebration of an event.
* Annually: Happening every year.
* Annuity: A sum of money paid to someone each year.
Less Common Words:
* Biennial: Happening every two years.
* Centennial: Happening every one hundred years.
* Millennial: Happening every one thousand years.
* Perennial: Lasting for many years, or occurring year after year.
* Sesquicentennial: Happening every one hundred and fifty years.
Note: There are some words that contain the sound "ann" but don't actually derive from the root "ann," such as "announce" and "annul."
Hope this helps!