The words printers use
A printer's spec sheet is short, flat and unhelpful to a newcomer. It assumes you already know what a leaf is, what bulk does to a spine, and why nobody will quote you an odd page count.
None of these words are hard. They are trade words, and a trade rarely stops to define them. Here they are in groups, with a line on what each is and why it matters to you.
Pages and sheets
Leaf. One physical piece of paper in the book. It carries two pages, one on each side, which is the fact behind everything else here.
Page. One side of a leaf. When a printer says 300 pages they mean 150 leaves.
Recto and verso. The right-hand and left-hand page. Recto is always odd-numbered, and chapters traditionally open on one.
Extent. The total page count, cover excluded. It drives spine width, gutter and price.
Signature. A large sheet printed with many pages and folded into a section, commonly sixteen or thirty-two. It is why books from a press run come in round page counts.
Why the count is always even. Every leaf has two sides, so a page count cannot be odd, and blanks are added to make it work. Blank pages, recto and verso, and why the count is even has the rules for where those blanks land.
Size and position
Trim size. The finished size of the book after the stack is cut. Everything else on the sheet is measured from it. See Choosing a trim size.
Bleed. Artwork extended past the trim so a slightly off cut still lands on ink. The standard is 0.125 in on outside edges, and never at a spine fold.
Safe area. The margin inside the trim where nothing important may sit — about 0.25 in — because the cut moves a little on every copy. Bleed and safe area, explained once is the whole story.
Gutter. The inner margin, at the binding. It has to grow with page count because a thick book does not open flat: up to 300 pages needs 0.5 in, rising to 1.0 in past 828. See Margins and gutters.
Creep. In a folded and stapled book, the inner pages push outward and are trimmed shorter than the outer ones. It affects saddle-stitched work only, and shifts page numbers toward the edge if ignored.
Paper
Stock. The paper itself. Print on demand offers a short fixed menu rather than a catalog.
Basis weight and gsm. Two ways to state how heavy a sheet is. Pounds depend on the grade weighed, so they do not compare across grades; grams per square meter always do.
Bulk and PPI. Bulk is thickness per page; PPI is pages per inch, the same fact inverted. It sets spine width — KDP white runs 0.002252 in per page, cream 0.0025, and Lulu simply divides pages by 444. See How to calculate spine width.
Opacity. How little you see of the next page through this one. Not the same property as weight, and the one that decides whether your book reads cleanly: Paper weight, opacity and show-through.
Grain direction. The way the fibers line up in the sheet. Grain should run parallel to the spine; against it the book resists opening, which readers feel without knowing why.
Coated and uncoated. Coated stock has a surface layer that holds ink crisply and suits images; uncoated is the ordinary novel paper that takes a pen and does not glare.
In the tools. The Cover Maker draws live trim, bleed and safe-area guides and computes the spine from the real page count, paper color and printer, so the geometry on the spec sheet is applied rather than measured by hand. Start your book → · about the tools
Ink and color
Four-color process. Full color built from cyan, magenta, yellow and black. It is how every photographic cover is printed, and why screen colors shift on paper: Why your cover prints darker than it looked.
Spot color. A single ink mixed to a specified reference rather than built from four. Exact and consistent, and generally a print-run option rather than a print-on-demand one.
Black only. A one-ink interior, the standard for a text book and much cheaper than color: Color inside the book, and what it costs.
Halftone, screen and tint. Continuous tone is reproduced as a field of dots of varying size; a tint is a percentage of an ink rather than a solid, and very light tints can vanish on uncoated stock.
Registration. How precisely the inks line up with each other. Slight misregistration is why fine colored type on a colored field looks fuzzy in print and sharp on screen.
Binding
Perfect binding. Pages glued to a wrapped cover at a squared-off spine: the ordinary paperback.
Case binding. A text block bound into rigid boards: a hardcover. Endpapers glue the block to the boards, the hinge is the flexing joint where the cover opens, and a headband is the woven strip at each end of the spine. Endpapers, headbands and the parts of a hardcover takes those apart properly.
Saddle stitch. Folded sheets stapled through the fold. Cheap and flat-opening, but viable only at low page counts.
Sewn. Signatures stitched with thread before binding. Stronger than glue alone and better opening, which is why it is specified for books meant to last.
Lay-flat. Any binding that stays open on a table unheld — for cookbooks, manuals and music: Books that need to lie flat. For what each binding does to your cover file, see Paperback, hardcover, dust jacket: what changes.
Finishing
Lamination, matte or gloss. A thin film bonded to the cover. Gloss saturates color and shows fingerprints; matte is softer and can scuff pale.
Spot UV. A glossy varnish applied to selected areas only, usually over matte, so a title catches the light.
Foil, emboss and die-cut. Metallic stamping, raised impression, and a shaped cut through the board. All three are print-run finishes rarely offered on demand: Foil, embossing and other cover finishes.
Production
Proof. A copy made for approval before the book goes on sale. Order one and read it: Order the proof. Then read it in daylight. It is a sample of the file, not a specimen later copies are matched against — Why your proof and your production copies differ.
Preflight. The automated check on your files before printing — fonts embedded, resolution, bleed, page count. It is what rejects you: Preflight: what to check before you upload.
Imposition. Arranging pages on the press sheet so they fall in order once folded. The printer does it; you meet the word only when a proof comes back scrambled.
Make-ready. Setting a press up for a specific job. It is a fixed cost paid once, which is the whole reason a long run gets cheaper per copy: Print on demand or a print run?
Overs and unders. A run delivers slightly more or fewer copies than ordered, within an agreed tolerance, and you are billed for what arrives — one of the lines that catches people out in Reading a print quote.
Print run. A fixed quantity manufactured at once, as against printing each copy when it sells.
With those in hand a spec sheet stops being prose and becomes a list of numbers you can check against your own file, which is the point.
Make your book
The tools are free to use: name your book, bring your manuscript or your artwork, and work as long as you like. You only pay when you want the files without the preview watermark.
Next: The printer's template, and how to read it · More: Why print files get rejected, and how to not be rejected · Book cover dimensions, start to finish · How print-on-demand actually works