A more thorough explanation:

Definition: A direct line is a line of descent traced through only those persons who are related to each other directly as ascendants or descendants.

For example, if we trace the direct line of descent of a person, we only consider their ancestors and descendants who are directly related to them. This means we do not include collateral relatives, such as cousins or aunts and uncles.

Another example of a direct line is in business. A company may have a direct line of products, which are closely related and often part of the same product line. For instance, a clothing company may have a direct line of winter wear, which includes coats, hats, and gloves.

Overall, a direct line refers to a clear and direct connection between related individuals or products.