A more thorough explanation:

Definition: Medium filum is a Latin term that refers to the middle line of a stream of water, which supposedly divides it into two equal parts and usually constitutes the boundary between the riparian owners on each side. It is also known as filum aquae.

Example: If two people own land on opposite sides of a river, the medium filum is the imaginary line that separates their properties. Each owner has the right to use the water up to the medium filum, but not beyond it.

This term is commonly used in legal cases involving water rights and boundaries. It is important to determine the medium filum to avoid disputes between landowners.