Luculent is an adjective that means clear in thought or expression.

The Latin word lux (LOOX) which means ‘light.’ provides the basis for many words related to illumination and clarity including lucid and our word of the day luculent. It’s been a part of the English language since the mid 16th century.

My earliest term papers could not exactly be described as luculent. They were so lacking in clarity that my professors accidentally thought they were brilliant.