difference between over and for

Question

I have a simple question.

over centuries / for centuries

what is the difference?

Thank you.

Answer 1

For implies constancy, while over implies change. Here are some examples:

Over centuries the English language has evolved.

For decades America has remained the world's greatest superpower.

Sometimes both forms are acceptable:

He has been constantly learning new information over/for the last few years.

The fact that he is learning means that there is change (in his amount of knowledge), and therefore over should be used. However, the rate of change remains the same, suggesting for as the correct word. In this case both are fine.