1. the quality or power of emitting or giving off light, heat, or radiation
Usage: technical; physics
2. in particle physics, a measure of the spread or divergence of a beam of particles
Usage: technical; physics

Examples

• The emittance of the heated metal increased as its temperature rose.
• Engineers measured the thermal emittance of the new coating material.
• The laser's emittance determines how tightly focused the beam can be.
• Different surfaces have different emittance values depending on their composition.
• The particle accelerator was designed to minimize beam emittance.