A more thorough explanation:

Definition: Filacium is a Latin word that means "thread". It has different meanings depending on the context:

1. It refers to a thread or wire that holds legal papers together to form a file. This was the ancient method of filing legal papers.
2. It can also refer to an imaginary thread or line passing through the middle of a stream or road. This line is used to divide the stream or road into two equal parts and is usually the boundary between the riparian owners on each side.
3. It can also refer to the border of a forest or the middle line of a road.

Examples:

• Example 1: In the past, legal papers were held together by a filacium, which was a thread or wire that kept them organized in a file.
• Example 2: The filum aquae is an imaginary line that divides a stream into two equal parts. It is used to determine the boundary between the riparian owners on each side of the stream.
• Example 3: The filum viae is the middle line of a road, which can also be used to determine the boundary between landowners on each side of the road.

These examples illustrate how filacium can have different meanings depending on the context. In the first example, it refers to a thread or wire used to hold legal papers together. In the second example, it refers to an imaginary line used to determine the boundary between riparian owners. In the third example, it refers to the middle line of a road, which can also be used to determine the boundary between landowners.