Describes language, explanations, or reasoning that is easy to understand and free of obscurity. Often used in formal or written contexts.
His explanation was clear and could be understood by anyone.
この本は平明な文章で書かれている。
This book is written in plain, simple language.
plain and lucid; articulate
Composed of 平 (flat, plain) and 明 (bright, clear). The combination suggests something that is level and bright, hence easy to see and understand.