Final answer:
In Shakespeare's Sonnet 18, "Nor lose possession of that fair thou owest;" means not letting go of one's own beauty.
Step-by-step explanation:
In Shakespeare's Sonnet 18, the line "Nor lose possession of that fair thou owest;" means that one should not let go of the beauty that they possess.
This line emphasizes the importance of holding on to one's own beauty and not allowing it to fade away. It suggests that the beauty one possesses is a treasure that should be cherished and preserved.
By using the word "possession," Shakespeare conveys the idea of ownership and implies that beauty is something personal and unique to each individual.