Fluoride is the reduced form of the element fluorine. Flouride is a halide ion, which means it bears a negative charge.

Fluoride ions are found in several minerals, particularly flourite. Flouride salts are used extensively in industrial chemicals, especially to produce hydrogen fluoride for fluorocarbons. The fluoride ion is structurally similar to the hydroxide ion.
 

Some examples of compounds that contain flouride include:

• Inert compound calcium fluoride
• Reactive fluoride sulfur tetrafluoride
• Medications such as efavirenz
• Toxins or poisons such as Sarin
• Inorganic fluorides such as hydrofluoric acid (HF), sodium fluoride (NaF), and uranium hexafluoride (UF6)
• Commercially important fluorides such as fluorite and fluorapatite

Usually, these compounds contain covalent bonds that bind the fluorine and hence they are called fluorides. Fluorides are different from other halides such as chloride in terms of reactivity and can be more strongly solvated due to a small radius to charge ratio. While other silyl halides are easily hydrolyzed, the Si-F linkage is one of the stronger bonds that is not easily broken or hydrolyzed.

Trace amounts of fluoride occur naturally in drinking water and foods. While underground sources of water are richer in fluoride content, seawater contains, on average, around 1.3 parts per million (ppm). Fresh water supplies do not contain more than 0.01–0.3 ppm of fluoride. One of the main features of fluoride is its ability to maintain the health of teeth and it is therefore added to many brands of toothpaste and to drinking water in a process called fluoridation.