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The title of this question says it all.
Are there nouns for longer periods than a millennium ?

I mean words designating a specific number of years.

Era, age and epoch don't count as they just indicate a period of time (possibly quite long) that is not counted in years, but that is defined by of a characteristic of that period.
(E.g the "Age of the Dinosaurs" was a fair number of millions of years, but not a specific number.)

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I wonder if this might be better off on ELU? – JMB Jan 10 at 20:54
@JMB I wasn't sure either. Posted it here as it was such a basic question. – Tonny Jan 11 at 15:41

There is presently nothing that comes next.

Some terms referenced do have year values assigned to them (Epoch at 1,000,000 years and Aeon at 1,000,000,000 years) but common usage relates to geological time periods which are not consistent in length.

Once beyond millennia we use numbers of years such as "One Hundred-Thousand Years", or some use metric prefixes to 'annum' (for example megaannum as referenced in Wikipedia) but they are basically the same idea. To follow the same principle from a Latin root form (as Decade, Century etc are latin) then `Decem millennium' (10,000 years) would arguably be closest to our existing words but it would be unlikely to see common use.

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I wasn't aware of "annum". Now that I am, I can't but help wondering if this would be understood by a the general public. I certainly haven't heard/seen this before. I asked a friend who is a professional interpreter/translator and she didn't know the term either. – Tonny Jan 11 at 15:47
@Tonny - No, "annum" is not a common term, particularly in the way it's used in "megaannum". I would say don't use it when writing for the general public. – stangdon Jan 11 at 15:58

The next stop after millennium is terasecond
For rounded number of years, it's megaannum

An interesting table can be found here

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