first, earliest or original / (biology) characteristic of the earliest stage of the development of an organism, or relating to a primordium / primeval

A first principle or element.

Hypothermia caused by exposure to a cold environment.

plural of prime number

(informal, evolutionary theory) The state of the Earth's oceans at a very early time in the planet's history, during the early development of multicellular organisms.

Alternative form of prime time

(chemistry) any compound of general formula R-PH₂

(philosophy) The initial agent that is the cause of all things.

plural of prima ballerina

(scholarly studies) An original work, especially one by a notable author whose work is now the subject of commentaries (secondary sources).