Fluoride

How to spell fluoride

8 letters · 2 syllables

How to pronounce fluoride

Say the part in capitals loudest.

What does fluoride mean?

1. nounA compound of fluorine, especially the form added to drinking water and toothpaste to help prevent tooth decay.

Fluoride in a sentence

• The dentist recommended a toothpaste with a higher fluoride content.

• The local council voted to add fluoride to the public water supply.

Where does fluoride come from?

Language of origin: Latin

This word grows out of the chemistry of fluorine, whose name traces back to the Latin verb fluere, meaning 'to flow'. The connection comes from the mineral fluorspar (calcium fluoride), which early metalworkers added to ores because it lowered their melting point and helped the molten metal flow more freely; in effect it acted as a flux, another relative of the same Latin root. When chemists in the nineteenth century isolated and named the element fluorine, they kept that 'flowing' reference, and the suffix -ide was then attached to mark a compound of that element with another, exactly as in chloride, oxide, and sulphide. So fluoride literally names 'a compound of fluorine'. The spelling trap lives in the opening cluster: the vowels run f-l-u-o, an order that feels backwards to many adults who want to write 'flouride'. Remembering the link to 'fluorine' and to fluere, 'to flow', keeps the u-before-o sequence in the right place.

How the word is built

• fluor- (from fluorine, ultimately Latin fluere 'to flow')
• -ide (chemistry suffix for a binary compound)