Trim size refers to the final dimensions of a printed book or document after it has been cut and finished. It is an important aspect of book design, as it affects the layout, readability, and overall appearance of the publication. Common trim sizes for books include 5.5 x 8.5 inches for trade paperbacks and 6 x 9 inches for standard novels. Choosing the right trim size can influence printing costs and distribution options. Publishers often select a trim size that aligns with market standards and reader preferences, ensuring that the book is visually appealing and easy to handle.