If you use a computer, chances are you know what a font is. It’s a typeface — or is it? Not according to the traditional definition. Arial Bold is a typeface. However, according to the traditional definition, 12 point Arial Bold is a font. Back when type was cast out of metal, type foundries sold type in a variety of sizes, each considered a separate font.
Today when computer users speak of fonts, they mean a typeface in its entire range of sizes.
A typeface is a set of letters, numbers and symbols designed to share common characteristics such as style, thickness and height. A typeface family consists of typefaces that are variations on a particular typeface. For example, variations on Arial could include: regular, black and narrow, as well as their italic variations. Each variation was considered a different typeface, and each size was considered a separate font.
The two main type classifications are serif type and sans-serif type. The French word “sans” which prefaces sans-serif means “without” — it designates type lacking serifs. So, just what is a serif? A serif is a small finishing flourish, somewhat resembling a notch made by a chisel to make a carved letter stand out better upon stone. These flourishes are found at the tops and bottoms of letters. Typically, a vertical stroke on a letter has a horizontal serif, while a horizontal stroke has a vertical serif.
There are two additional type categories in addition to serif and san-serif type; script and display. Script typefaces look like handwriting and range from wedding invitation elegance to quickly jotted casualness. Display fonts, which may or may not have serifs, are designed to be used in headlines and typically consist of all capital letters.
Type is grouped by the styles that were popular in different eras. A few examples include: Old Style, such as Garamond and Caslon; Transitional, such as Baskerville; Modern, such as Bodoni; Sans-Serif, such as Arial and Avant Garde. Designers differentiate type by considering the characteristics of each of its parts, as well as the degree of vertical or horizontal stress, contrast or lack of contrast, etc.
Type size is highly variable. For example, 72 points is a measurement equal to one inch. However, a 72 point font won’t necessarily appear to occupy one inch. This is because a font is measured both by its letterforms and by the white (or empty) space surrounding its letterforms. The white space at the tops and bottoms of letters prevents a line of type from running into the lines above and below.
When type was cast out of metal, a degree of empty space at the tops and bottoms of letters was necessary due to the technology used.
In addition to the amount of white space above and below letters, other factors determine the appearance of type. All type sits on a baseline, but the baseline height can vary in its vertical placement.
One useful type measurement is the x-height (also known as the body). The x-height is the height of a lowercase letter x. The feet of the x rest on the baseline. Anything below the baseline, such as the bottom portion of the letter p, is called the descender. Anything rising above the hands of an x, such as the top portion of the letter d, is called the ascender. The term cap height refers to the height of an unrounded capital letter from the baseline to its top. Rounded capital letters, such as O, or pointed letters such as A, can extend slightly beyond the cap height, just as rounded lower case letters can extend somewhat above the x-height or below the baseline. Lower case ascenders are often taller than the cap height.
Excerpt from Graphics Essentials for Small Offices.