Ailing

pellucid \puh-LOO-sid\, adjective:

1. Transparent; clear; not opaque.
2. Easily understandable. 

The prevailing atmosphere as one cruises Kukulcan Boulevard, the busy strip where most of Cancun's 122 hotels are clustered, remains that of an Orlando or a Las Vegas dropped intact next to pellucid Caribbean waters.
-- Larry Rohter, "What's Doing in Cancun.", New York Times, March 8, 1998

In her scrupulous and pellucid prose, she appears to distance herself from the optimistic Californian light.
-- Cynthia Ozick, "What Writer's Writers Write.", New York Times Magazine, January 2, 2000

Pellucid comes from Latin pellucidus, "shining, transparent," from pellucere, "to shine through," from per-, "through" + lucere, "to shine."