used to show how far sth is true or how great an effect it has :
To a certain extent , we are all responsible for this tragic situation.
He had changed to such an extent (= so much) that I no longer recognized him.
To some extent what she argues is true.
The pollution of the forest has seriously affected plant life and, to a lesser extent , wildlife.
To what extent is this true of all schools?
The book discusses the extent to which (= how much) family life has changed over the past 50 years.