Far infrared is a term that refers to the longer wavelength infrared radiation that is produced by the sun, as well as objects such as heaters and saunas. There are several synonyms for the word "far infrared," including long wave infrared, thermal infrared, and far IR. These terms are commonly used in scientific research and industrial settings, where infrared radiation is used for various purposes such as heating and cutting materials. Far infrared radiation is also often used in medical applications, such as for pain relief and wound healing. No matter what it's called, far infrared radiation has a wide range of uses and benefits.