Which definition best describes opaque?

• A. Not letting light pass through; not transparent or translucent
• B. Difficult to understand or explain
• C. Clearly understood
• D. Transparent

Answer: (A)

Opacity describes something that blocks light, so it cannot be seen through; it’s not transparent or translucent. This physical sense is the most universal and primary meaning of the word, which is why it’s the best fit here. The idea of something being opaque can also be used metaphorically to mean difficult to understand or explain, but that is a secondary nuance. The opposite of opaque is transparent, and saying something is clearly understood mixes the notion of comprehension with a different sense of clarity, not the material property.