fluor(o)-

Also fluo‑.

Fluorine; fluorescence.

Latin fluor, a flux, from fluere, to flow.

The mineral fluorspar was so called because it was used as a flux in metal working; the element fluorine was first isolated from it. Organic chemical compounds that contain fluorine and chlorine are chlorofluorocarbons, now known to be largely responsible for the depletion of the ozone layer in the upper atmosphere; fluorine compounds are added to toothpastes and drinking water to help harden teeth, by a process called fluoridation, but excess of it can lead to fluorosis, marked by a mottling of the teeth.

Some names for inorganic fluorine compounds mark the presence of fluorine with fluo‑, as in fluoborate or fluosilicate.

Some substances exhibit fluorescence, emit light when they are irradiated with radiation such as ultra-violet; the phenomenon was so named because it was first demonstrated in fluorspar. Several words beginning in fluoro‑ refer to it: fluorography is photography in which the image is formed through fluorescence; a fluoroscope has a screen that fluoresces when hit by X-rays, so the image can be viewed directly; fluorimetry is a method of analysis using fluorescence.