同級
どうきゅう · doukyuu · JLPT N1 · noun
class
同 (same) + 級 (grade, rank): same grade, same class
同 means same and 級 means grade or rank, so 同級 describes people at the same level, such as classmates in one grade.
同 — 冂 enclosure + 一 + 口 mouth
Originally depicted multiple mouths gathered under one cover or enclosure, suggesting people speaking together in agreement. From this image of voices joining, it came to mean 'same,' 'together,' or 'alike.' The shared cover symbolizes unity.