An em (from em quadrat ) is a unit in the field of typography, equal to the currently specified point size. For example, one em in a 16-point typeface is 16 points. Therefore, this unit is the same for all typefaces at a given point size. [1]
The em space is one em wide.
Typographic measurements using this unit are frequently expressed in decimal notation (e.g., 0.7 em) or as fractions of 100 or 1000 (e.g., 70⁄100 em or 700⁄1000 em). The number of pixels per em varies depending on system.
In metal type, the point size (and hence the em, from em quadrat ) was equal to the line height of the metal body from which the letter rises. In metal type, the physical size of a letter could not normally exceed the em.
A digital font's design space in digital type is called the em, which is a grid with arbitrary resolution. Scaling the em to a particular point size is how imaging systems—whether for screen or print—work.
In digital type, the relationship of the height of particular letters to the em is arbitrarily set by the typeface designer. However, as a very rough guideline, an "average" font might have a cap height of 70% of the em, and an x-height of 48% of the em. [2]
In some older texts, but not all, the em is defined, or said to have been defined, as the width of the capital 'M' in the current typeface and point size. [3] Possibly, this is because the 'M' (or 'm') sort in such cases cast the full-width of the quad (also known as em quad, mutton quad, or m quadrat); and thus, the width of the sort would equal its point size. [4]
Note however, that in the oldest attested English text from 1683 mentioning em (as m or m quadrat), this alternative definition is not used, and also not in many other older texts. [5] [6]
In Cascading Style Sheets, the em unit is the height of the font in nominal points or inches. The actual, physical height of any given portion of the font depends on the user-defined DPI setting, current element font-size, and the particular font being used.
To make style rules that depend only on the default font size, another unit was developed: the rem. The rem«rem Unite», or root-em, is the font size of the root element of the document. Unlike the em, which may be different for each element, the rem is constant throughout the document. [7]
Typography is the art and technique of arranging type to make written language legible, readable and appealing when displayed. The arrangement of type involves selecting typefaces, point sizes, line lengths, line spacing, letter spacing, and spaces between pairs of letters. The term typography is also applied to the style, arrangement, and appearance of the letters, numbers, and symbols created by the process. Type design is a closely related craft, sometimes considered part of typography; most typographers do not design typefaces, and some type designers do not consider themselves typographers. Typography also may be used as an ornamental and decorative device, unrelated to the communication of information.
Type design is the art and process of designing typefaces. This involves drawing each letterform using a consistent style. The basic concepts and design variables are described below.
A typeface is a design of letters, numbers and other symbols, to be used in printing or for electronic display. Most typefaces include variations in size, weight, slope, width, and so on. Each of these variations of the typeface is a font.
In typography, kerning is the process of adjusting the spacing between characters in a proportional font, usually to achieve a visually pleasing result. Kerning adjusts the space between individual letterforms while tracking (letter-spacing) adjusts spacing uniformly over a range of characters. In a well kerned font, the two-dimensional blank spaces between each pair of characters all have a visually similar area. The term "keming" is sometimes used informally to refer to poor kerning.
Dots per inch is a measure of spatial printing, video or image scanner dot density, in particular the number of individual dots that can be placed in a line within the span of 1 inch (2.54 cm). Similarly, dots per centimetre refers to the number of individual dots that can be placed within a line of 1 centimetre (0.394 in).
In typography, leading is the space between adjacent lines of type; the exact definition varies.
An en is a typographic unit, half of the width of an em. By definition, it is equivalent to half of the body height of the typeface. The en is sometimes referred to as the "nut", to avoid confusion with the similar-sounding "em".
In typography, the point is the smallest unit of measure. It is used for measuring font size, leading, and other items on a printed page. The size of the point has varied throughout printing's history. Since the 18th century, the size of a point has been between 0.18 and 0.4 millimeters. Following the advent of desktop publishing in the 1980s and 1990s, digital printing has largely supplanted the letterpress printing and has established the desktop publishing (DTP) point as the de facto standard. The DTP point is defined as 1⁄72 of an inch (1/72 × 25.4 mm ≈ 0.353 mm) and, as with earlier American point sizes, is considered to be 1⁄12 of a pica.
The font family selection in (X)HTML, CSS, and derived systems specifies a list of prioritized fonts and generic family names; in conjunction with correlating font properties, this list determines the particular font face used to render characters. The family selection is available in two forms: in the deprecated (X)HTML <font>...</font>
element with its face
attribute, and in the CSS font-family
property.
In typography, the x-height, or corpus size, is the distance between the baseline and the mean line of lowercase letters in a typeface. Typically, this is the height of the letter x in the font, as well as the letters v, w, and z. One of the most important dimensions of a font, x-height defines how high lowercase letters without ascenders are compared to the cap height of uppercase letters.
Letter spacing, character spacing or tracking is an optically consistent typographical adjustment to the space between letters to change the visual density of a line or block of text. Letter spacing is distinct from kerning, which adjusts the spacing of particular pairs of adjacent characters such as "7." which would appear to be badly spaced if left unadjusted, and leading, the spacing between lines.
In graphic design, a grid is a structure made up of a series of intersecting straight or curved lines used to structure content. The grid serves as an armature or framework on which a designer can organize graphic elements in a rational, easy-to-absorb manner. A grid can be used to organize graphic elements in relation to a page, in relation to other graphic elements on the page, or relation to other parts of the same graphic element or shape.
A whitespace character is a character data element that represents white space when text is rendered for display by a computer.
In metal typesetting, a font is a particular size, weight and style of a typeface. Each font is a matched set of type, with a piece for each glyph. A typeface consists of various fonts that share an overall design.
In typography, line length is the width of a block of typeset text, usually measured in units of length like inches or points or in characters per line. A block of text or paragraph has a maximum line length that fits a determined design. If the lines are too short then the text becomes disjointed; if they are too long, the content loses rhythm as the reader searches for the start of each line.
In typography, a column is one or more vertical blocks of content positioned on a page, separated by gutters or rules. Columns are most commonly used to break up large bodies of text that cannot fit in a single block of text on a page. Additionally, columns are used to improve page composition and readability. Newspapers very frequently use complex multi-column layouts to break up different stories and longer bodies of texts within a story. Column can also more generally refer to the vertical delineations created by a typographic grid system which type and image may be positioned. In page layout, the whitespace on the outside of the page are known as margins; the gap between two facing pages is also considered a gutter, since there are columns on both sides.
Typeface anatomy describes the graphic elements that make up letters in a typeface.
Typefaces are born from the struggle between rules and results. Squeezing a square about 1% helps it look more like a square; to appear the same height as a square, a circle must be measurably taller. The two strokes in an X aren't the same thickness, nor are their parallel edges actually parallel; the vertical stems of a lowercase alphabet are thinner than those of its capitals; the ascender on a d isn't the same length as the descender on a p, and so on. For the rational mind, type design can be a maddening game of drawing things differently in order to make them appear the same.
The Monotype system is a system for printing by hot-metal typesetting from a keyboard. The two most significant differences from the competing Linotype machine are that
In typography, a quad was a metal spacer used in letterpress typesetting. The term was later adopted as the generic name for two common sizes of spaces in typography, regardless of the form of typesetting used. An em quad is a space that is one em wide; as wide as the height of the font. An en quad is a space that is one en wide: half the width of an em quad.
Quads were no doubt originally square spaces, as broad as the height of a line. From the fact that the letter m (or M) used to be cast on a square body, such a square space is called an em-quad.