Typeface anatomy describes the graphic elements that make up letters in a typeface or font (a specific size, slope, and style of a typeface).
Strokes
The strokes are the components of a letterform. Stroke shape in many typefaces is influenced by historical methods of writing, such as the shape of a tool, the angle at which it is applied, and the degree of pressure used.
Terminology Strokes may be straight, as in , or curved, as in . If straight, they may be horizontal, vertical, or diagonal; if curved, open or closed. Typographers also speak of an instroke, where one starts writing the letter, as at the top of , and an outstroke, where the pen leaves off, as at the bottom of .
A main vertical stroke is a stem. The letter has three, the left, middle, and right stems. The central stroke of an is known as the spine. When the stroke is part of a lowercase and rises above the height of an (the x height), it is known as an ascender. Letters with ascenders are . A stroke which drops below the baseline is a descender. Letters with descenders are .
An arching stroke is a shoulder as in the top of an or sometimes just an arch, as in . A closed curved stroke is a bowl in ; has two bowls. A bowl with a flat end as in is a lobe. A trailing outstroke, as in is a tail. The inferior diagonal stroke in is a leg. The bottom of the two-story is a loop; the very short stroke at the top is the ear. The letters each have a dot or tittle.
A short horizontal stroke, as in the center of and the middle stroke of , is a bar. Strokes that connect, as in and , or cross other strokes, as in , are also known as crossbars. A longer horizontal stroke at the top or bottom, as in , is an arm. The junction of two strokes intersecting above as in is an apex and the joining of two strokes intersecting below as in is a vertex.
Stress or contrast The font shown in the example is stressed; this means that strokes have varying widths. In this example, the stroke at the top of the "g" is thinner at the top and bottom than on the sides – a vertical stress. Fonts without any variation in the stroke width are known as monoline fonts. Stress is also known as contrast. Reverse-contrast typefaces flip the normal convention of which strokes should be thin vs. thick.
Weight
The weight of a particular font is the thickness of the character outlines relative to their height.
A typeface may come in fonts of many weights, from ultra-light to extra-bold or black; four to six weights are not unusual, and a few typefaces have as many as a dozen. Many typefaces for office, web and non-professional use come with a normal and a bold weight which are linked together. If no bold weight is provided, many renderers (browsers, word processors, graphic and DTP programs) support a bolder font by rendering the outline a second time at an offset, or smearing it slightly at a diagonal angle.
The base weight differs among typefaces; that means one font may appear bolder than another font. For example, fonts intended to be used in posters are often bold by default while fonts for long runs of text are rather light. Weight designations in font names may differ in regard to the actual absolute stroke weight or density of glyphs in the font.
Attempts to systematize a range of weights led to a numerical classification first used in 1957 by Adrian Frutiger with the Univers typeface: 35 Extra Light, 45 Light, 55 Medium or Regular, 65 Bold, 75 Extra Bold, 85 Extra Bold, 95 Ultra Bold or Black. Deviants of these were the "6 series" (italics), e.g. 46 Light Italics etc., the "7 series" (condensed versions), e.g. 57 Medium Condensed etc., and the "8 series" (condensed italics), e.g. 68 Bold Condensed Italics. From this brief numerical system it is easier to determine exactly what a font's characteristics are, for instance "Helvetica 67" (HE67) translates to "Helvetica Bold Condensed".
The first algorithmic description of fonts was made by Donald Knuth in his 1986 Metafont description language and interpreter.
The TrueType font format introduced a scale from 100 through 900, which is also used in CSS and OpenType, where 400 is regular (roman or plain).
The Mozilla Developer Network provides the following rough mapping to typical font weight names: Names Numerical values Thin / Hairline Ultra-light / Extra-light Light Normal / regular Medium Semi-bold / Demi-bold Bold Extra-bold / Ultra-bold Heavy / Black Extra-black / Ultra-black
Font mapping varies by font designer. A good example is Bigelow and Holmes's Go Go font family. In this family, the "fonts have CSS numerical weights of 400, 500, and 600. Although CSS specifies 'Bold' as a 700 weight and 600 as Semibold or Demibold, the Go numerical weights match the actual progression of the ratios of stem thicknesses: Normal:Medium = 400:500; Normal:Bold = 400:600".
The terms normal, regular and plain (sometimes book) are used for the standard-weight font of a typeface. Where both appear and differ, book is often lighter than regular, but in some typefaces it is bolder.
Before the arrival of computers, each weight had to be drawn manually. As a result, many older multi-weight families such as Gill Sans and Monotype Grotesque have considerable differences in weights from light to extra-bold. Since the 1980s, it has become common to use automation to construct a range of weights as points along a trend, multiple master or other parameterized font design. This means that many modern digital fonts such as Myriad and TheSans are offered in a large range of weights which offer a smooth and continuous transition from one weight to the next, although some digital fonts are created with extensive manual corrections.
As digital font design allows more variants to be created faster, a common development in professional font design is the use of "grades": slightly different weights intended for different types of paper and ink, or printing in a different region with different ambient temperature and humidity. For example, a thin design printed on book paper and a thicker design printed on high-gloss magazine paper may come out looking identical, since in the former case the ink will soak and spread out more. Grades are offered with characters having the same width on all grades, so that a change of printing materials does not affect copy-fit. Grades are common on serif fonts with their finer details.
Fonts in which the bold and non-bold letters have the same width are "duplexed".
Variable fonts are computer fonts that can store and use a continuous range of weight (and size) variants of a single typeface.
Terminals
The terminal (end) of an instroke or outstroke is often a serif or a stroke ending. A seriffed terminal may be described as a wedge, bulbous, teardrop, slab serif, etc., depending on the design of the type. Typefaces may be classified by their look, of which the weight and serif style – whether serif or sans-serif – are key features. Some designs also have spurs, which are smaller than serifs and appear on angles rather than at a terminal, as on or .
Serif typefaces are also known as antiqua, and slab serif is known as Egyptian. Typefaces without serifs are known as sans serif ( means "without" in French) or (or, in German, ).
Great variety exists among both serif and sans-serif typefaces. Both groups contain faces designed for setting large amounts of body text, and others intended primarily as decorative.
Typefaces with serifs are often considered easier to read in long passages than those without. Studies on the matter are ambiguous, suggesting that most of this effect is due to the greater familiarity of serif typefaces. As a general rule, printed works such as newspapers and books almost always use serif typefaces, at least for the text body. Websites do not have to specify a font and can simply respect the browser settings of the user. But of those web sites that do specify a font, most use modern sans-serif fonts, because it is commonly believed that, in contrast to the case for printed material, sans-serif fonts are easier than serif fonts to read on the low-resolution computer screen.
Some font superfamilies incorporate both serif and sans-serif or even intermediate slab serif or semi-serif fonts with the same base outlines. A more common font variant, especially of serif typefaces, is that of alternate capitals. They can have swashes to go with italic minuscules or they can be of a flourish design for use as initials (drop caps).
Space Areas of negative space (white space) enclosed by strokes are called counters or counterforms. Closed counters are found in , and open counters in . The closed counter in is also named an eye. The term storey refers to stacked counters: When the letter a appears with two counters it is referred to as double-storey a, and when the letter g appears with two closed counters it is known as double-storey .
Angles of white space, as in , are corners ( has three corners); the term is not used for angles of strokes. The small corner formed by a serif, whether curved or angular, is called the serif bracket.
Inter-letter space can be reduced with kerning. A kern is the part of a letter that intrudes into the "box" of an adjacent glyph.
Geometric ratios
A subtle change in proportion impacts weight, perception, measure, and legibility. The letterform height compared to its stroke width modifies the aspect ratio; a slight change in weight sometimes helps to create emphasis. The disparity between thick and thin strokes, known as stress, alters optical perception. As an example, the first sans serif typefaces used strokes of constant thickness, but subsequent technological advances permit drawing thinner strokes. Condensed type occupies less space than expanded type, so that a whole page of text can be reduced to half a page. The capline and x-height ratio improve or decrease word legibility.
Character width
Fixed vs. variable
A proportional typeface, also called variable-width typeface, contains glyphs of varying widths, while a monospaced (non-proportional or fixed-width) typeface uses a single standard width for all glyphs in the font. Duospaced fonts are similar to monospaced fonts, but characters can also be two character widths instead of a single character width.
Most typefaces either have proportional or monospaced (for example, those resembling typewriter output) letter widths, if the script provides the possibility. Some superfamilies include both proportional and monospaced fonts. Some fonts also provide both proportional and fixed-width (tabular) digits, where the former usually coincide with lowercase text figures and the latter with uppercase lining figures.
Many people generally find proportional typefaces nicer-looking and easier to read, and thus they appear more commonly in professionally published printed material. For the same reason, GUI computer applications, such as word processors and web browsers, typically use proportional fonts. However, many proportional fonts contain fixed-width (tabular) numerals so that columns of numbers stay aligned.