main pillar; newel post
In architecture, the principal pillar of a structure, or the central post of a staircase (newel post).
The newel post of the staircase is decorated.
The main pillar of this building is designed to be especially thick.
「親」は主要なもの、中心的なものを表し、「柱」と組み合わさって主要な柱を意味する。建築分野で使われる複合語。