The following table is adapted from the scale of the American Library Association,[1][13] in which size refers to the dimensions of the cover (trimmed pages will be somewhat smaller, often by about 1⁄4 inch or 5 mm[2]). The words before octavo signify the traditional names for unfolded paper sheet sizes. Other dimensions may exist as well.[4][14] US Trade size corresponds with octavo and is popular for hardbacks.