IPA: //daɪˈæfənəsnəs//
KK: /daɪˈæfənəsnəs/
The quality of being very thin and transparent, allowing light to pass through.
The diaphanousness of the fabric made it perfect for a summer dress.
Diaphanousness is formed from "dia-" (meaning through) and "phanous" (from Greek "phaneros", meaning visible or clear) combined with the suffix "-ness" (meaning the state of being). The word describes the quality of being light, delicate, and transparent, allowing light to pass through.
Think of something that is 'clear' or 'visible' ('phanous') and allows light to pass 'through' ('dia-') — that's what diaphanousness means.
No commonly confused words.