first dan; lowest black-belt rank; shodan
The initial dan rank in martial arts (judo, karate, kendo, etc.) and board games (go, shogi). It is the first step above kyu grades and is often considered the beginning of serious study. In some contexts, it can simply mean the lowest rank.
彼は柔道で初段を取った。
He earned his first dan in judo.
囲碁
A first dan in Go still has a lot to learn.