Formality fit describes how well a fabric's visual and tactile properties match the expected aesthetic of a dress code. High formality fit (0.8-1.0): silk, wool, cupro, cashmere. Low formality fit (0-0.4): denim, canvas, jersey, polyester. Formality fit is the key differentiator when two fabrics have similar thermal performance: in a tropical business-formal context, lyocell and linen are ranked by formality fit, not breathability alone.