The difference between Crystal clear and Pellucid

When used as adjectives, crystal clear means completely clear and understood, whereas pellucid means allowing the passage of light.

check bellow for the other definitions of Crystal clear and Pellucid

Crystal clear as an adjective (idiomatic):

Completely clear and understood.

Examples:

"Reread through the manual until the instructions are crystal clear in your head."
Crystal clear as an adjective (idiomatic):

Visually clear, a sharp image, high acuity.

Examples:

"The picture on this TV is crystal clear – you can see every grain of sand!"