Learner's definition of EXTENT
1 : the range, distance, or space that is covered or affected by something or included in something
She tried to determine the extent of the damage.
the full extent of human knowledge
They underestimated the extent [=size] of the problem.
He questions the extent to which these remedies are needed.
2 : the point or limit to which something extends or reaches
We reached the southernmost extent [=end] of the peninsula.
He swore to prosecute them to the fullest extent of the law. [=as fully as the law allows]
To what extent [=how far, how much] can they be trusted?
◊ If you say that something is true to an extent, to some extent, or to a certain extent, you mean that it is partly but not completely true.
To an extent, they're both right.
Some critics claim that the government is at fault, and, to a certain extent, that's true.
Something that is true to a large extent or to a great extent is mostly true.
The phrases to the extent that, to that extent, and to a greater/lesser extent are often used to describe the effect or importance of something in relation to something else.
To the extent that he encouraged their bad behavior, he's to blame for it. [=he's partly to blame for their bad behavior because he encouraged it]
He encouraged their bad behavior, and to that extent he's to blame for it.
He studied only to the extent that was required to pass the exam. [=he studied just enough to pass the exam]
This new tax affects the middle class and, to a lesser extent, the rich.
This new tax affects everyone to a greater or lesser extent. [=it affects some people more than it does other people]
— used to indicate the degree to which something exists, happens, or is true
To the extent that or to such an extent that can also be used to say that something is true to a very extreme degree.