IPA: /ˈsʌb.tɪl.nəs/
KK: /sʌbˈtaɪl.nəs/
The quality of being delicate, fine, or subtle in nature or appearance.
The subtileness of the fabric made it perfect for the elegant dress.
Subtileness is formed from "subtilis" (meaning fine or delicate) and the suffix "-ness" (meaning the state or quality of). The word refers to the quality of being fine or delicate in nature.
Think of something that is 'fine' or 'delicate' ('subtilis') and how that quality is described by the suffix '-ness'.