It is called nine centuries.
There is no widely used term for such a period.
A quarter century.
That 1000 years is called the Middle Ages, medieval period, or even Age of Faith.
period
You may be thinking of a "score", as in Lincoln's Gettysburg Address ('Four score and seven years ago' means 87 years ago.)It is also called two decades.
Every four years. This period of time was called an "olympiad".
A Period of ten years is called a decade.
A period of 75 years is called a "septuagenary."
A period of 10 years is called a decade.
A period of 100 years is called a century.
A period of 100 years is called a century.
A period of ten years is a decade.
The period of 100 years is called a century. A period of 10 years is a decade, and 1000 years is a millennium.
The four years between two summer games or between two winter games is called an olympiad. Note that the summer and winter games are separated by two years, e.g. 2008 Beijing, then 2010 Vancouver and then 2012 London.
It is called a recession. If it lasts longer than three of four years it is called a depression.
A period of forty years is called a quadragennial.