If you’re conscientious, you think carefully about the words you choose, whether it’s an email message or a formal report. Making yourself clearly understood helps you get your message across and helps your readers benefit from what you’re saying.

Many people, however, don’t think twice about the way their words, specifically their letters, look on screen or paper. The particular form that letters take involves the font you choose. And the art of choosing the right font is called typography.

The meaning of the word “font” has changed over the years; in the digital world today it’s largely synonymous with “typeface,” meaning a stylistically coordinated set of letters, numbers, and punctuation marks. Typography has been around for far longer than personal computers, but PCs have opened up typographic possibilities to far more people.

When desktop publishing was introduced in 1985, the surfeit of font choices led many people to create documents that looked like ransom notes written by a terribly inspired 10-year-old. At the opposite extreme is always using the same font, which isn’t much different from always wearing the same clothes. People make judgments about you and what you’re writing as a result of the font you use, even if those judgments are subconscious.

The two most popular fonts today are Times New Roman and Arial, the former being a “serif” font (with small designs at the ends of strokes within letters) and the latter being a “sans serif” font (which lacks such designs). Sans serif fonts, which are starker and bolder, are more commonly used for titles and headlines, while serif fonts can aid legibility and are more commonly used for the body of works.

People typically choose among the fonts that their computer programs install for them. But you can also buy fonts separately, with there being literally tens of thousands available. You can also visit websites where generous designers make fonts available to download for free, including 1001 Free Fonts (www.1001freefonts.com).

Choosing which font makes the most sense for any given work is much like choosing which clothes to wear to work, a formal party, an informal gathering of friends, or a workout at the gym. You should aim for image and utility.

A study by researchers at the Software Usability Research Laboratory of Wichita State University sheds light on this. The researchers analyzed 20 of the more common fonts by asking more than 500 people their views about the images the fonts projected. The best font for projecting flexibility was Kristen, assertiveness was Impact, practicality was Georgia, and creativity was Gigi. But as there are usually two sides to a coin, Kristen also projects instability and rebellion, Impact rudeness and unattractiveness, and Gigi impracticality and passiveness.

Some people use Courier New because it’s a monospaced font, meaning each letter takes up the same amount of horizontal space, just as with a typewriter. It’s useful if you need to align numbers in a column. But Courier New can project conformist, unimaginative, and dull, according to the researchers. A better choice for a monospaced font is Consolas.

Times New Roman is a versatile, all-around font with an interesting history. It was commissioned by the British newspaper The Times in 1931, hence its name. Microsoft has included it in every copy of Windows since version 3.1, and it’s the default font in many Windows programs. On the Mac it’s called Times, and it’s also the default in many Mac programs. The U.S. State Department in 2004 mandated that all U.S. diplomatic documents use Times New Roman instead of the previous Courier New. But if you use it reflexively, consider Georgia, which is less stiff but equally legible.

Even though the Wichita State study looked at only 20 fonts, reading its results (available at http://psychology.wichita.edu/surl/usabilitynews/81/personalityoffonts.htm) can give you a good feel for why type talks.

Fonts can be fun, but don’t overdo them. One rule of thumb is use at most three different fonts per page. You should also minimize the use of varying font sizes and styles, such as italic, bold, and underline. Too much variety can be jarring to the eye.

Also avoid long stretches of text in italic, bold, or uppercase, which can be more difficult to read than regular upright type (Roman). Similarly, make sure there’s enough contrast between the letters and their background. Black on white is easier to read than white on black, and both are easier to read than green on blue. The most legible combination is black on cream.