In Jain cosmology, a jav (yava) is a traditional unit of measurement used to describe extremely small distances or sizes, especially when explaining the dimensions of atoms (paramanu) and other minute entities.

Definition of 1 Jav (Yava):

• A jav refers to the length of a barley grain, which was a common standard of measurement in ancient India.
• In Jain texts, a 1 jav is often used as a reference point to further subdivide into even smaller units when describing the size of souls (jiva), atoms, or particles (paramanu).

Hierarchy of Smallest Measurements in Jainism:

1. Angula (finger breadth)
2. Yava (barley grain)
3. Liksha (louse egg)
4. Ratharenu (dust particle)
5. Paramanu (indivisible atom)

For example, according to Jain texts:

• 7 liksha = 1 yava (jav)
• 7 yava = 1 angula

In summary: 1 jav (yava) is the length of a barley grain and is an important unit in Jain cosmological measurements, used to explain the gradation from observable sizes down to the subtlest, indivisible paramanu.

If you want more details about how these measurements are used in Jain cosmology—such as in describing the universe or the soul—please specify!