Why is the U.S Constitution called a living document?

Answer 1

because it can change at any time. All it takes is the required amount of states to ratify an amendment and the constitution changes. Older amendments can be overturned as well. So the U-S Constitution is something that can change, not something that is carved in stone and unchangeable.
Because the added amendments breathe new life into it.

Answer 2

It has changed with time
because it can change at any time. All it takes is the required amount of states to ratify an amendment and the constitution changes. Older amendments can be overturned as well. So the U-S Constitution is something that can change, not something that is carved in stone and unchangeable.
Because the added amendments breathe new life into it.
It is called a living document because it can be changed when it needs to be changed.
First of all, it is still used and relied on for an entire country of 300 million+ people. Secondly, and probably more relevant to this question, it is being changed. It can be ammended, and the way it is interpreted can change over time. Because it is not stagnant and it can change with time, it is considered a living document.