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.
He earned his first dan in judo.
囲碁の初段は、まだまだ勉強が必要だ。
A first dan in Go still has a lot to learn.