What term describes mammals that produce living young from within the body?

The term that describes mammals that produce living young from within the body is "viviparous." This characteristic distinguishes them from other reproductive strategies, such as laying eggs. In viviparous mammals, fertilization occurs internally, and the developing fetus is nourished directly through a placental connection or similar structure, allowing for greater protection and provision of nutrients during development.

Oviparous, on the other hand, refers to organisms that lay eggs, which develop outside the mother's body. Endothermic and exothermic relate to temperature regulation in animals rather than their reproductive strategies. Endothermic animals, known as warm-blooded, maintain a constant body temperature through metabolic processes, while exothermic animals depend on external environmental conditions to regulate their body temperature. Thus, the designation of mammals that give birth to live young is uniquely defined by the term viviparous.