Level

Mid-frequency: not on every page, but regular in books and magazines.

More common than 壁 (Wall), less common than 困 (Distressed).

A thread (糸) climbs an escalator (及) — each step up the escalator represents a new level of skill, threaded together.

In words

級きゅう class, grade, rank,school class, gradeN3

高級こうきゅう high class,high gradeN2

上級じょうきゅう advanced level,high grade,seniorN2

級 is rank 789 of 2,608 in published Japanese.