HSK Guide

Radical 2a vertical stroke; a line drawn straight down

gǔn (third tone, dipping)

a vertical stroke; a line drawn straight down

Radical 21 stroke1 characters

Where the shape comes from

Not a word anyone speaks — it is the downward stroke itself, which the Shuowen glosses as movement up and down a line. It survives only as an index heading, and it takes characters built on a strong central axis: 中, 丰, 串.