坳
Definition
* 山间的平地。 山～。～口（山或丘陵间的较低处，多为穿过山岭的通道）
a hollow in the ground, a cavity, depression; undulating, depressed
Structure
Related substructures
Precursors
Small Seal Script
Standardized 221–206 BCE (Qin); developed earlier in Qin
The standardized seal script promulgated after Qin’s unification, based on earlier Qin seal forms and used as an empire-wide norm.Wikipedia ->
Liushutong Seal Forms
Pre-Qin to Han seal-type forms (≤220 CE) / compiled 1661 (Min Qiji); collated and printed 1720 (Bi Hongshu)
A ten-volume compendium of seal-script variants arranged by the rhymes of Hongwu Zhengyun: each head character gives its Shuowen small seal form, then variants gathered from guwen, zhouwen, bronze inscriptions and Qin–Han seals. Long a standard reference for seal carvers, but the forms are compiled rather than excavated and were collected with little vetting, so many are of doubtful authenticity.Wikimedia Commons ->