palaios

Palaios is a Greek adjective meaning ancient or old. In scientific terminology, palaios forms the basis of the widely used prefix palaeo- (also spelled paleo-), which signals antiquity and is used to denote topics or time scales from the distant past. The prefix appears across the geosciences and life sciences, including palaeontology (the study of ancient life), palaeobotany, palaeoecology, palaeoclimatology, and palaeogeography.

Regarding spelling, palaeo- is the form common in British English, while paleo- is standard in American English; both derive from the same Greek root. The prefix is used in many modern terms to describe ancient organisms, environments, and geological processes.