Does it mean
from year 1995 to year 1999 or
from 1995 to 2004?
Can you explain some more usages of the word
Edit: Source is here
Radiation therapy was used less frequently in the decade after 1994 than in the prior.
The only sense which could be expected is from 1994 or 1995 to 2004.
If someone meant 1995-1999 then they would have to say something like "the rest of the decade after 1995."
You don't usually see 'decade' used this way, but you do often see sentences with "in the decade following [an event in 1994]". In that case it means the next ten years, from 1994-2004.
So a sentence might say something like:
In the decade after the 1994 World Cup, the popularity of women's soccer grew exponentially in the United States
That means that the popularity grew between the summer of 1994 (after the World Cup ended) and the summer of 2004 (10 years later).
A decade is just a period of ten consecutive years. It's not restricted to periods where the first three digits of the year are the same, such as the 1980s.
They've given us several boundaries to determine the meaning. "After 1994" isn't inclusive, so our starting point is 1995. Since our start date doesn't end in zero, it rules out "a period of ten years starting and ending in zero" leaving us with 1995-2004.
The phrase "than in the prior" should mean 1985-1994 since this would be "a ten year period" adjacent to and before the 1995-2004 decade.