The Latin for year is ann, anni, annu, and enni which is how we get annual or yearly. Somehow the habit of calling it the one year anniversary of an event has crept into the language regularly.-one year and annual both mean the same thing. The word anniversary comes from Latin anniversaries “returning annually” from annus “year” and vertere “to return”. It is curious how these habits start, we don’t talk about our one year annual income or our one year annual plants which grow for just one year. And then just to confuse matters there is biannual (occurring twice a year) and biennial (occurring every two years). Enough ranting for one day there are many such annoying habits I could go on and on!