Dagger and double dagger - symbols used mainly as reference marks for footnotes.

Densitometer - a device for measuring the Optical density at a specific location on film or printed product, either by reflected or transmitted light. Densitometers vary in their sophistication and the number of features provided, such as colour, black-and-white, read-out memory, computer printout etc.

Desktop publishing - a generic title given to the introduction of personal computers (PC) to typesetting, page composition and image handling. The combination of all these gives electronic control within a single system of what was traditionally a specialist and segmented operation.

Die - a hardened steel engraving stamp used to print an inked image. Used in the production of good quality letter headings.

Digital - describes the use of digital pulses, signals or values to represent data in computer graphics, telecommunications systems and word processing.

Digital page composition - DPC, also known as EPCS (electronic page composition system) or CEPS (colour electronic page system). A system designed to take a range of page elements (text, line-work and images) and integrate them into a user-specified format. Image and text input to the system arrive on magnetic tape, by direct system interconnection or directly from an input scanning system.

Display type - larger type used for headings etc. Normally about 18 point or larger.

Digital Colour Proofs - A colour proof produced from digital -data.  Digital proofs may be Pre-RIP (before rendering pixels), or Post—RIP.  Low resolution proofs are generally used to check content only and High resolution to check colour matching.

Dithering - A technique of filling the gap between two pixels with another pixel having an average value of the two to smooth out the resulting image.

Dot - The individual element in both halftones and four colour process printing.

Dot Gain - In printing, a defect in which dots print larger than they should, causing darker tones and stronger colours.

Doubling - Printing defect appearing as blurring or shadowing of the image. Doubling may be caused by problems with paper, cylinder alignment, blanket pressures or dirty cylinders.

Dot matrix printer - a printer in which each character is formed from a matrix of dots. They are normally impact systems, ie a wire is fired at a ribbon in order to leave an inked dot on the page, but thermal and electro-erosion systems are also used.

Double density - a method of recording on floppy disks using a modified frequency modulation process that allows more data to be stored on a disk.

Double page spread - two facing pages of newspaper or magazine where the textual material on the left hand side continues across to the right hand side. Abbreviated to DPS.

Downloadable fonts - type faces which can be stored on a disk and then downloaded to the printer when required for printing. These are, by definition, bit-mapped fonts and, therefore, fixed in size and style.

DPI (Dots Per Inch) - the measurement of resolution for page printers, phototypesetting machines and graphics screens. The greater the DPI, the finer the print.

Drawn on - a method of binding a paper cover to a book by drawing the cover on and gluing to the back of the book.

Drawn-on cover - A paper book cover which is attached to the sewn book by gluing the spine.

Drop cap - a large initial letter at the start of the text that drops into the line or lines of text below.

Drop-Out - Fine halftone dots or fine lines which are eliminated from the highlight areas of the plate during the platemaking process.

Dry transfer (lettering) - Characters, drawings, etc, that can be transferred to the artwork by rubbing them off the back of the transfer sheet. Best known is Letraset.

Dummy - A sample of a proposed job made up with the actual materials and cut to correct size to show bulk, style of binding, etc. Also a complete layout of a job showing position of type matter and illustrations, margins etc.

Duotone - a halftone picture made up of two printed colours.

Duplex Cutting - operation of converting a web paper into sheets on a cutting machine equipped with two cross-cut knives so that two different lengths of sheet can be cut simultaneously.