1. plural of emittance; the fraction of thermal radiation emitted by a surface compared to that emitted by an ideal black body at the same temperature.
Usage: technical; physics
2. plural of emittance; in particle physics, a measure of the spread of particles in a beam in both position and momentum.
Usage: technical; particle physics

Examples

• The emittances of different materials vary depending on their surface properties and temperature.
• Engineers calculated the thermal emittances of the spacecraft's exterior panels.
• High emittances are desirable for radiators designed to dissipate heat efficiently.
• The emittances of the electron beam were measured to optimize accelerator performance.
• Surface coatings can significantly alter the emittances of materials used in thermal systems.