noun, counter
school grade; school year; class
School-related use for a grade/year or class. Often seen in compounds or formal labels such as 同級 or 各級; everyday speech may use 学年 or クラス depending on context.
彼とは小学校で同級だった。
He and I were in the same grade at elementary school.
この学校では、各級に担任が一人いる。
At this school, each class has one homeroom teacher.
noun, suffix
Used as a noun or suffix to mark class, quality, rank, or skill level in a grading system. Common in compounds such as 初級, 上級, 高級, and A級.
この問題は初級の学習者には少し難しい。
This problem is a little difficult for beginner-level learners.
彼女は上級クラスに進んだ。
She advanced to the upper-level class.
noun, counter
kyu rank; junior rank
Domain-specific ranking term used in martial arts, go, shogi, and similar systems. It is counted with numbers, and in many systems 級 ranks are below 段 ranks.
See also: 段
彼は空手で一級を取った。
He earned first kyu in karate.
将棋で二級から一級に上がった。
I moved up from second kyu to first kyu in shogi.