Glossary P

pair kerning

In digital and phototypesetting, kerning based on the principle of adding or subtracting units of space between individual pairs of characters. Units added or subtracted typically consist of small divisions of the em. See also kerning.

p height

The distance from the baseline to the bottom of the lowest descender in a typeface. Also called descender depth.

phototype

Typefaces reproduced by photographic means (phototypesetting or photocomposition). In early technologies of phototype a beam of light passed through a film negative and exposed characters onto light-sensitive film or paper. More recently, however, some authors have also used phototype to refer to digital type that is reproduced on photographic paper. See also digital type.

pica

In the traditional Anglo-American point system used in measuring type, a unit equal to 12 points or roughly 1/6 inch (.166 inch or 4.2154 millimeters). In software for desktop publishing, usually rounded to exactly 1/6 inch. Picas are generally used to express the length of a line of text or the depth of page, as in a line of 22 picas or a page that is 40 picas deep. Also, describes a monospaced typewriter face that sets with 10 characters to the inch and 6 lines per inch. In the Didot point system (used in continental Europe), the equivalent unit is the cicero. At present there is no official standardization of the measurement of the traditional pica. Its dimension varies among different manufacturers and countries. See also point.

pi character

A character from an assorted collection of characters that are not necessarily related to a specific typeface. Includes symbols, reference marks, logos, mathematical and monetary symbols, and decorative elements. From a metal type term for an assortment of characters that has been indiscriminately mixed. In machine composition with metal type, pi characters were not assigned key positions but rather had to be inserted by hand. Also known as special sorts, and in the U.K., peculiars.

piece fraction

A term from metal type for fractions that are made up of multiple pieces or keystrokes: for example, in metal type the diagonal fraction bar and the numerator or denominator are typically one piece, the denominator or numerator (whichever has not been paired with the fraction bar), the other. Different from case fractions, which in metal type were usually created by the type manufacturer as complete characters. Also known as split fraction.

Also sometimes used to refer to fractions in digital type; although in this technology the fraction bar is usually a separate character, rather than being joined with the numerator or denominator. In this usage, similar to built-up fraction or composite fraction, which also refer to fractions composed from multiple pieces in computer-aided typography. See also built-up fraction, composite character.

pi font

A font comprising versions of symbols and typographic elements that are not necessarily related to a specific typeface. May include reference marks, logotypes, decorative elements, mathematical and monetary symbols, and other characters. See also pi character.

pixel

A picture element, the smallest unit of a digital image, as displayed on a computer screen, paper, or other presentation surface. In representing type on screen, usually a square or rectangular dot; in print, usually round or oval.

point

A unit used to measure type, typically applied to the vertical height or size of typefaces and characters and to the space between baselines (line spacing or interlinear space). Traditionally equal to roughly 1/72 inch but varies in size among different countries and manufacturers. In the Anglo-American point system, one point typically equals .01383 inch (.351282 millimeter); in the Didot (French) system, it equals .01483 inch (.376682 millimeter).

In desktop publishing, usually rounded to exactly 1/72 inch. See also pica, point size. In the U.K., and sometimes in the U.S., point (or full point) also refers to the period; points to punctuation marks in general.

point size

A measure used to identify the size of composed type. Based on the traditions of metal type, in which the depth of the block of metal on which letters rested determined type size, not the height of the letters themselves.

Due to variations in the relative proportions of letters in different typefaces (principally lowercase letters), and in digital type especially, to differing methods for defining the body of the typeface, the same point size from different typefaces may vary in apparent size. To be absolutely sure of typeface dimensions, type designers, compositors, and graphic designers sometimes refer to measurements of character heights, such as the H height (capital height), x-height, kp height (distance from the highest ascender to lowest descender), Eˆp height (distance from the highest accented capital to lowest descender), Ep or Hp height (distance from the highest capital to the lowest descender, relevant when when capitals are taller than ascenders), and p height (descender depth). See also body, point.

proof

In type design, a sample of a character, word, or typeface, printed for study and correction of its overall effect, the appropriateness of character design, weight, alignment, spacing, size, suitability for a specific printing technology, and other features. Also known as typeface test, and in the U.K., as trial, trial proof. In typesetting and graphic design, also refers to a sample of copy or of a design used for proofreading and correction. See also keywords.

proportionally spaced typeface

A typeface in which characters occupy individually determined or fitted widths, as opposed to a monospaced typeface, in which characters have identical widths. Most Latin typefaces are proportionally spaced. See also fit, fitted, monospaced typeface.

punctuation

The use of standard marks in written communication to clarify the meaning or intent of a message. Examples of punctuation marks include the period, comma, question mark, and quotation marks.

punctuation space, punctuation width

A fixed space whose width is equal to that of the space occupied by the period or comma.