自行
zì xíng · HSK 7
by oneself
🚶 自 self + 行 go/act = act on your own = voluntary, by oneself
自 means self and 行 means to go or act, so 自行 is to do something self-propelled, without being told. It marks an action taken voluntarily or autonomously, and as a prefix it works like English self- (self-acting).
自 — pictograph of a nose
自 originally depicted a human nose, shown frontally with the bridge and nostrils. Ancient Chinese pointed to their own nose to mean 'me,' so 自 shifted to mean 'self' or 'oneself.' A new character 鼻 was later created to carry the original 'nose' meaning.
行 — crossroads pictograph (left 彳 + right 亍)
行 originally pictured a four-way crossroads in oracle bone script, with two paths meeting. From 'road' it extended to 'walk, go, travel,' and then to 'a row, line' or 'business firm' (read háng). The two halves 彳 and 亍 are the split sides of that ancient crossroads.