(1) Apt to cause trouble or be unruly. (2) Stirring up quarrels; irritable.

One of the earliest meanings of *fraction* was “a breakin good feeling”—that is, an argument or conflict. So a person who starts fights could be called fractious. A fractious horse is one that hasn't been properly broken or trained. A fractious political party is one whose members keep fighting among themselves. And a fractious baby is one that's always breaking the home's peace and quiet with angry squalling.

An irregular shape that looks much the same at any scale on which it is examined.

This term was coined in 1975 to describe shapes that seem to exist at both the small-scale and large-scale levels in the same natural object. Fractals can be seen in snowflakes, in which the microscopic crystals that make up a flake look much like the flake itself. They can also be seen in tree bark and in broccoli buds. Coastlines often represent fractals as well, being highly uneven at both a large scale and a very small scale. Fractal geometry has been important in many fields, including astronomy, physical chemistry, and fluid mechanics. And even some artists are benefiting, creating beautiful and interesting abstract designs by means of fractals.

The breaking of a law or a violation of another's rights.

An infraction is usually the breaking of a law, rule, or agreement. So a nation charged with an infraction of an international treaty will usually have to pay a penalty. In Federal law, an infraction is even smaller than a misdemeanor, and the only penalty is a fine. Most of us occasionally commit infractions of parking laws and get ticketed; speeding tickets are usually for infractions as well, though they go on a permanent record and can end up costing you money for years to come. The closely related word *infringement* generally refers to a violation of a right or privilege; use of another's writings without permission, for example, may be an infringement of the copyright.

The root of *refraction* is seen in the notion that the path of a ray of light or wave of energy is “broken” when it is deflected or turned. The effects of refraction can be seen in a rainbow, which is formed when light rays passing into (and reflecting out of) water droplets are bent at different angles depending on their color, so that the light separates into bands of color. The amount of refraction depends on the angle and the type of matter; refraction can occur even when passing through different kinds of air. A mirage, such as you might see in the desert or over a patch of asphalt in the summer, occurs when light passing through warm air meets the very hot air near the surface; reflecting the sky, it often resembles a lake.

Well-suited to appear on television, especially by having an appearance and manner attractive to viewers.

The word *telegenic,* a blend of “*tele*vision” and “photo*genic,*” first appeared back in the 1930s, before hardly anyone owned a TV. With the supreme importance of TV cameras in politics, people running for political office today worry about being telegenic enough to have a successful career. Even events have been described as telegenic; unfortunately, such events are often human tragedies, such as fires, earthquakes, or floods, which happen to broadcast well and capture the interest of the viewers.

Showing or relating to design or purpose, especially in nature.

*Teleology* has the basic meaning “the study of ends or purposes.” So Aristotle's famous “teleological argument” claims that anything complex must have a creator, and thus that God exists. And a teleological explanation of evolutionary changes claims that all such changes occur for a definite purpose. But the type of morality called “teleological ethics” doesn't involve God at all: instead, it claims that we should judge whether an act is good or bad by seeing if it produces a good or bad result, even if the act involves harming or killing another person.

Telemetry is used to obtain data on the internal functioning of missiles, rockets, unmanned planes, satellites, and probes, providing data on such factors as position, altitude, and speed as well as conditions like temperature, air pressure, wind speed, and radiation. Weather forecasters rely on telemetry to map weather patterns. Astronauts on the space shuttle are monitored with telemetry that measures and transmits readings on their blood pressure, respiration, and heart rates. Similar kinds of telemetry are used by biologists to study animals in the wild and keep track of their populations and movements. Telemetry is also widely used in modern agriculture, often to regulate irrigation.

To work at home using an electronic link with a central office.

This word has been around since the early 1970s, when computer terminals in the home first began to be connected to so-called mainframe computers by telephone lines. Since the creation of the World Wide Web in 1991, and with the widening access to broadband connections, telecommuting has grown to the point that the U.S. is now home to many millions of occasional *telecommuters*. Telecommuting can make work much easier for people with young children and people with disabilities, and because of its obvious environmental benefits and the lessening of traffic congestion, telecommuting is now officially encouraged by federal legislation. Still, only a fraction of those who could be telecommuting are actually doing so.