Decade is 10 years, century 100, millennium 1000 - is there a word for 10,000?
Decamillenium? 
According to this, it goes from millennium (1,000 years) to epoch (1,000,000 years).
Decamillenium = 10,000 years
Centamillenium = 100,000 years
Myriad, which functions both as noun and adjective, means “10,000” (not specifically years). So “[a] myriad [of] years”, with the “a” and “of” optional, would do the job.
Also, if you’re curious it continues as follows:
megennium = 1 million years
decamegennium =10 million years
centamegennium = 100 million years
gigennium = 1 billion years
I think only geologists ever really use these terms, though.
Is 2,000,000 years a tupoch?
1,000,000,000 years is an eon (which I’ve never seen written æon in this context). It’s a specialized usage, of course.
And 10,000,000 is a shakur.
Takes a lot of balls to make that joke.
:d&r
And if a lot happens during that million years, it’s an epic epoch.
Normal English would be to say “10 milliennia”.
The metric prefix for 100 is hecto, not centa.
It’s not metric, it’s Latin.
Going on what Diogenes the Cynic said, I’m pretty sure:
Year = 1 year
Decade = 10 years
Century = 100 years
Millenium = 1,000 years
Decamillenium = 10,000 years
Centamillenium = 100,000 years
Megennium = 1 million years
Decamegennium =10 million years
Centamegennium = 100 million years
Gigennium = 1 billion years
Decagigennium = 10 billion years
Centagigennium = 100 billion years
Terrennium = 1 trillion years
Decaterrennium = 10 trillion years
Centaterrennium = 100 trillion years
petennium = 1 quadrillion years
Decapetennium = 10 quadrillion years
Centapetennium = 100 quadrillion years
Exennium = 1 quintillion years
Decaexennium = 10 quintillion years
Centaexennium = 100 quintillion years
Zettennium = 1 sextillion years
Decazettennium = 10 sextillion years
Centazettennium = 100 sextillion years
Yottenium = 1 septillion years
Decayottenium = 10 septillion years
Centayottenium = 100 septillion years
However, this is just another post extended and I could be completely wrong:confused:.
In India, everyday language uses lac (100,000) and crore (10,000,000) when referring to money. An Indian financier will say “ten lac” rather than “one million” rupees, and then “five crore” rather than “fifty million”. Commas are used differently for separators. Instead of $12,345,678 expressed as millions, it will be $1,23,45,678, and said "one crore, 23 lacs, 45 thousand "