"centennial" vs. "centurial" - describing periods of 100 years

Question

I'm interested in describing a record that spans multiple hundreds of years.

My writing partner suggests referring to this as "a centurial record of __", though intuition tells me that "a centennial record of __" may be more natural.

I fell that centennial is more appropriate because of its similarity to the language my (scientific) field uses for periods of 10s of years (decadal) and periods of 1000s of years (millennial).

Merriam-Webster provides the following definitions:

"centurial" (adj): relating to 100 years

"centennial" (noun): a 100th anniversary or its celebration

Though MW also indicates that "centennial" can be used as an adjective.

So my questions are:

1. Are these words interchangeable?
2. Is one more appropriate than the other?
3. Are there other more common ways to describe something which spans hundreds of years?

Answer 1

1. I would not use centennial because it means the anniversary, the 100-year mark.
2. I would not use centurial because it is too little known. Nor does its meaning include what you intend.
3. Without knowing more of your context, I might suggest “centuries-long,” “centuries-old,” “spanning centuries,” or something like that.

Answer 2

As others have already explained, the word 'centennial' has already been bagged for a different purpose: that of a single celebration of something that has been going for a hundred years. The Cambridge English does not include the word 'centurial'. The American dictionary, Merriam Webster gives it the briefest of references, defining it again for a different use than that sought in the question.

relating to 100 years : marking or beginning a century, with the example "the centurial years 1600 and 1700".

But there is a word that is widely used to indicate the range of years or centuries covered by an article or book: history. There is a general expectation that, if history is of a restricted period of time, the time will be specified in some way. So 'The history of trousers in Edwardian England', The History of the British Isles from 1066, tells the reader the scope covered, whether more, as in my first example (where the coverage is from the date given to the date of publication), or less than a century (as in my second example).

If there is some strong reason for indicating the fact that more than one or less than one is covered, then the author can say so directly. The first known historian, Herodotus, used the word historia, which combined what we now call history with what we now would call ethnography. We derive from it, of course, the word story