At the dentist

Le canal radiculaire is « the root canal », and the gap between those two names is the most useful grammatical fact on the page. English builds a compound by standing one noun in front of another and leaving the relation between them unsaid: « root canal », « gum disease », « tooth decay », « mouth guard ». French does that only in a handful of fixed modern coinages and never on demand, so it has two ways round it, and this list uses both. The first is de with the second noun, which says out loud the relation the English compound kept silent: la dent de sagesse, the tooth of wisdom. The second is a relational adjective, and that is what radiculaire is — an adjective built on the Latin radix so that canal can be qualified instead of modified by a noun. It agrees, it follows its noun, and the page is full of them: la plaque dentaire, la gouttière occlusale, la radiographie panoramique. Notice that the adjective is learned where the noun is everyday, so French keeps both — la racine beside radiculaire, much as « root » sits beside « radical ».