1. Plural of emissivity; the measure of how effectively a surface emits thermal radiation compared to an ideal black body, expressed as a ratio between 0 and 1.
Usage: technical; physics; engineering

Examples

• Different materials have different emissivities depending on their surface properties and temperature.
• The emissivities of metals are typically lower than those of non-metallic materials.
• Engineers must account for the emissivities of various surfaces when designing thermal systems.
• Polished aluminum has a lower emissivity than oxidized aluminum.
• The emissivities of coatings can be measured using specialized infrared equipment.