“Lucidus” is Latin for “clear,” and “per” means “through,” so one definition of “pellucid” is “completely transparent.” Other words that share the “clear” Latin root include “translucent,” “lustrous,” “elucidate,” “illustrate,” and, of course, “lucid.” Another usage of “pellucid” is as a synonym of “lucid”: “expressed clearly; easy to understand.” The third usage is in a lyrical sense to describe beautifully clear tones and pure-sounding music.