Incorrect spelling


Incorrect spelling, explanation: because of the fact, that Latin original annus, a year, (genitive anni) is spelled with double n, the spelling in English is similar and we spell this word anniversary. Aniversary is a mistaken spelling and the correct one is anniversary.

Correct spelling


Correct spelling, explanation: anniversary is a word of Latin origin (from annus, a year). The original word is spelled with double n and so is the later English anniversary. Therefore aniversary is an incorrect spelling.

Definition of anniversary:
noun, a yearly celebration of an event (usually an important one)
There are some independence day anniversary celebrations in the city park today.
Next month is Jack’s first anniversary as a sober man. He is very brave and stubborn.