How to pronounce infrared

1 : situated outside the visible spectrum at its red end —used of radiation having a wavelength between about 700 nanometers and 1 millimeter. 2 : relating to, producing, or employing infrared radiation infrared therapy. 3 : sensitive to infrared radiation infrared sensors that detect body heat.

H is silent in many English words, for various reasons. Not all such words that have come into English from French still have a silent h, however. Over the centuries we have come to pronounce the h in words like horrible, hospital, host, human, and humour.