In thermodynamics, the "p/v constant" is a term often used to describe the relationship between the pressure (p) and volume (v) of a gas, assuming that the temperature and the number of moles of the gas remain constant. The p/v constant is also known as the "inverse proportionality constant" and is denoted by the Greek letter kappa (κ).
The formula p/v = κ is often used in thermodynamics, when the number of moles of a gas and the temperature are held constant. This is derived from the Ideal gas law PV=nRT where P is pressure, V is volume, n is number of moles, R is the ideal gas constant, T is temperature. When we keep number of moles constant and T constant the PV/T will be equal to a constant κ
It's important to note that when p and v are inversely proportional, the product of p and v is constant, so pv = κT which is also known as the ideal gas law at constant temperature.