The term that determines the quantity of inertia for an object is mass.

Here's why:

* Inertia is the tendency of an object to resist changes in its motion.

* Mass is a fundamental property of matter that measures its resistance to acceleration.

In simpler terms, the more massive an object is, the harder it is to get it moving or to stop it once it's moving. This resistance to change in motion is what we call inertia.

So, mass is directly proportional to inertia. The greater the mass, the greater the inertia.