annual
newyear or birthdays
Annular means 'happening once a year'
Biannual describes something that occurs twice a year, once every half year.
My company holds an annual meeting to discuss our goals and achievements for the year.
The Earth orbits the sun once per year (which is the definition of a year).
The Earth rotates on its axis (an imaginary line going through the centre of the earth from the North pole to the South pole) once every twenty-four hours, and it orbits the Sun once every year.
Earth revolves around the Sun once per year.
The Earth revolves around the sun exactly once per year (that is actually the definition of a year).
Annual
The proper phrase is "coming once a year." "Annually" could be used.
Of or pertaining to a year; returning every year; coming or happening once in the year; yearly., Performed or accomplished in a year; reckoned by the year; as, the annual motion of the earth., Lasting or continuing only one year or one growing season; requiring to be renewed every year; as, an annual plant; annual tickets., A thing happening or returning yearly; esp. a literary work published once a year., Anything, especially a plant, that lasts but one year or season; an annual plant., A Mass for a deceased person or for some special object, said daily for a year or on the anniversary day.
1860