I wrote:
>>  "Centurian" sounds just like "Centurion", who is a Roman army officer
>>  commanding a force of 100 men.
>>
>>  "Centenarian" is a person 100 years old.

Anna answered:
>I'm printing this and using it for show and tell in my Abnormal Psych class.
>We need examples of OCD.  And this one fits that bill to a T.

Words come naturally to me, and I write professionally. I'm also a good
proofreader. I enjoy language, and respect it. It's not that seeing
"centurian"
in place of "centenarian" gives me pain, or anything. Use it if you like.
I assumed you might be speaking English as a non-native, and might want to
know the normal usage.

(Peace back ...)

Susan