challenging

To a high degree; very difficult.

To a very high degree; very difficult.

Sufficiently difficult to be interesting or satisfying.

Difficult in a way that requires significant bodily effort.

To a moderate degree; quite difficult.

Difficult in a way that requires significant mental effort.

Difficult in a way that relates to the practical skills or mechanics of a subject.

To the necessary degree to be considered difficult.

Difficult in a way that relates to politics or government.

Difficult in a way that relates to education and scholarship.

Used to describe the state of being difficult in an interesting or enjoyable way.

To perceive or discover that something is difficult.

To cause something to become difficult or demanding.

Used when something turns out to be difficult over time or after experience.