In Jain cosmology, Purva is an extremely large unit of time.

It is used in the traditional Jain measure of vast cosmic time, and 1 Purva is much, much longer than years, yugas, or even many other large time units. Jain texts describe it as an immeasurable span used to express the age of souls, celestial beings, and ancient cosmic periods.

In short:

• Purva = a very huge ancient Jain time unit
• It belongs to the traditional Jain system of countless and enormous time measures
• It is not a practical everyday unit; it is a cosmic measure

If you want, I can also explain the full Jain time scale from samaya, avali, muhūrta, day, year, yojana, palya, and purva.