Correlated Color Temperature (CCT) describes the color appearance of a white light source by comparing it with the color of a heated reference radiator. It is expressed in kelvins (K): lower values appear warmer and higher values appear cooler. CCT does not measure light output or intensity. Typical descriptions include warm white, neutral white, and cool white, although the boundaries between these categories vary. CCT refers to appearance rather than spectral quality, color rendering, or efficiency. When selecting heavy-duty lighting, it should be considered together with environmental conditions, operator comfort, contrast, CRI, and the photometric performance of the complete lamp.