We sometimes call 50 years 5 decades, but half a centuryis more common.
50 years is known as a half-century.
Golden jubilee
Golden jubile
It's called a Semicentennial. http://en.wikipedia.org/wiki/Anniversary
A period of one year can be called a year, or astronomically speaking, a revolution.
There is no dedicated word for a period of 50 years
A ten year period is a decade.
a 12 month period is called a fiscal year, there is also a natural year.
A period of six months is called half a year.
Or menopause.
Yes until they reach menopause.
A period of 1 thousand year is called a millennium.
a five-year period is a quinquennium
It's called a decade.
A period of 100 years is called a century.