taru-adjective, adverb taking the 'to' particle
evident; clear; distinct; plain
A somewhat formal, literary word used to describe something that is unmistakably obvious or clearly distinguishable. Often appears as 歴然とした or 歴然と.
両者の差は歴然としている。
The difference between the two is clear.
証拠は歴然とそこにあった。
The evidence was plainly there.