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| English | Arabic |
| mutual exchange coefficient between two surfaces S1 and S1, when the radiance or luminance of S1 (or S2) is the same at all points and for all directions | معامل التبادل المشترك |
| self-exchange coefficient of a surface when its radiance or luminance is the same at all points and for all directions | معامل التبادل الذاتي |