relative difficulty; degree of difficulty
A slightly written or formal noun for how easy or difficult something is. Common in phrases such as 難易を問わず and 難易に応じて; 難易度 is often more natural when speaking of a specific difficulty level.
I looked at the relative difficulty of the questions and decided the order in which to solve them.
Participants are welcome regardless of experience or the difficulty of the course.
Anyone can join this course, regardless of its difficulty level.
The points awarded vary according to the difficulty of the question.