coïter

Coïter is the clinical, biological term for copulating — used in medical, veterinary, or zoological contexts, not in ordinary conversation, where avoir des rapports or faire l'amour is what people actually say.

• Ces deux espèces coïtent au printemps. — These two species mate in the spring.
• Le vétérinaire a observé les animaux coïter en captivité. — The vet observed the animals mating in captivity.
• Le manuel de biologie décrit comment les insectes coïtent. — The biology textbook describes how insects mate.

Coïter sounds clinical and slightly cold applied to humans in casual speech — a learner using it in an everyday sentence about people will sound like they're reading from a medical report.