Mâchoire vs. mandibule
While both mâchoire and mandibule can translate to jaw, they are not always interchangeable. Mâchoire is the common, everyday term, while mandibule is a more precise, scientific term primarily referring to the lower jawbone.
Mâchoire
A2Mâchoire is the general and most common term for jaw. It can refer to the entire jaw structure (both upper and lower) or just one part. It is used in everyday conversation for both humans and animals and often evokes the action of biting or chewing.
Le boxeur a une mâchoire d'acier.
(The boxer has a jaw of steel.)
Mon chien aime mâcher des os pour renforcer sa mâchoire.
(My dog likes to chew bones to strengthen his jaw.)
Il est tombé et s'est fait mal à la mâchoire.
(He fell and hurt his jaw.)
À force de serrer les dents, j'ai des douleurs dans la mâchoire.
(From clenching my teeth, I have pain in my jaw.)
Le lion a ouvert grand sa mâchoire avant de rugir.
(The lion opened its jaw wide before roaring.)
Mandibule
B2Mandibule is the specific, anatomical term for the lower jawbone. It is primarily used in medical, dental, and scientific contexts (like zoology or paleontology). Using it in casual conversation would sound unusually formal or technical.
Le chirurgien a dû opérer une fracture de la mandibule.
(The surgeon had to operate on a fracture of the mandible.)
En paléontologie, l'étude de la mandibule nous renseigne sur le régime alimentaire des dinosaures.
(In paleontology, studying the mandible informs us about the diet of dinosaurs.)
Le dentiste a pris une radio de ma mandibule pour vérifier l'alignement des dents.
(The dentist took an x-ray of my mandible to check the alignment of the teeth.)
L'articulation temporo-mandibulaire connecte la mandibule au crâne.
(The temporomandibular joint connects the mandible to the skull.)
La fourmi utilise ses mandibules pour découper les feuilles.
(The ant uses its mandibles to cut leaves.)
Summary
In short, use mâchoire for general, everyday discussions about the jaw of a person or animal. Use mandibule in formal, scientific, or medical settings when specifically referring to the lower jawbone. A doctor will diagnose a fracture de la mandibule, but the patient will tell their friends they se sont cassé la mâchoire.