(1) (capitalized) The Ten Commandments. (2) Any basic set of rules that must be obeyed.

In *decalogue* the root *deca-* is combined with *logos,* Greek for “word.” In the Biblical book of Exodus, the original Decalogue, or Ten Commandments, was handed to Moses by God atop Mount Sinai. In Jewish and Christian tradition, the Ten Commandments are regarded as laws handed down from the highest authority and as the foundation of morality. They include commands to honor God, the Sabbath day, and one's parents, and bans on worshiping images, swearing, murder, adultery, theft, lying about others, and envying what others have. Individuals have often had their own personal decalogues; Thomas Jefferson's “ten commandments” started off with “Never put off till tomorrow what you can do today.”

An athletic contest made up of ten parts.

*Decathlon* from *deca-* and *athlon,* “contest,” means “ten contests.” The ancient Greek Olympics held five-contest competitions, or *pentathlons*, that were based on the skills needed in battle. The modern Olympic decathlon, which was born in 1912, consists of the 100-meter run, 400-meter run, 1500- meter run, 110-meter high hurdles, javelin throw, discus throw, shot put, pole vault, high jump, and long jump. The original winner was the legendary Jim Thorpe, who would later be judged the greatest American athlete of the 20th century. And ever since, the Olympic decathlon winner has been called the finest all-around athlete in the world.

The *bel*in *decibel* honors the inventor of the telephone, Alexander Graham Bell. Decibels work on a logarithmic scale (you may need to look up *logarithm*), so 20 decibels is 10 times as strong as 10 decibels, and 50 decibels is 1,000 times as strong as 20 decibels. The decibel readings of some everyday sounds make for interesting comparisons. Whispers and rustling leaves usually register under 20 decibels, the average level of conversation is about 50 decibels, and noisy factories or office machinery may have decibel levels of 90 to 100. In the category of sounds between 100 and 120 decibels, which can eventually cause deafness, we find elevated trains, artillery—and rock concerts.

To reduce drastically or destroy most of.

Commanders in the Roman army took discipline seriously. Mutiny in the ranks was dealt with by selecting, through drawing lots, one soldier in every ten and making the other nine club or stone the unfortunate winner of this gruesome lottery to death. The *dec-* in *decimate* thus reflects this Roman practice, which was ordered by such well-known leaders as Crassus, Mark Antony, and Augustus. But over time, the word's meaning has shifted, and today it almost always describes great destruction or loss of life. So, for example, we can say that a wave of layoffs has decimated a company's workforce, the populations of some of Africa's greatest wild animals have been decimated by poaching, or aerial bombardment has decimated whole sections of a city. ## CENT **CENT**, from the Latin *centum,* means “one hundred.” A dollar is made up of a hundred *cents,* though other monetary systems use *centavos* or *centimes* as the smallest coin. A *centipede* has what appears to be a hundred feet, though the actual number varies greatly. But there really are a hundred years in a *century.*

A 100th anniversary or the celebration of it; a centennial.

A *centenary,* like its cousin *centennial,* is an anniversary. Thus, the year 2013 may mark the centenary of a town's founding, and the year-long calendar of public events that the town sponsors for the occasion—that is, the celebration of the anniversary—can also be called a centenary. Individuals have their own centenaries, which usually celebrate their births; thus, Gerald Ford's centenary will occur in 2013, and John Kennedy's in 2017. And if you live long enough to be a *centenarian,* you'll be around to join the celebrations.

Relating to a temperature scale in which 0° is the freezing point of water and 100° is its boiling point.

The centigrade scale is essentially identical to the *Celsius* scale, the standard scale by which temperature is measured in most of the world. Anders Celsius of Sweden first devised the centigrade scale in the early 18th *century.* But in his version, 100° marked the freezing point of water, and 0° its boiling point. Later users found it less confusing to reverse these two. To convert Fahrenheit degrees to centigrade, subtract 32 and multiply by 5/9. To convert centigrade to Fahrenheit, multiply by 9/5 and add 32.

A length measuring 1/100th of a meter, or about 0.39 inch.

In the metric system, which is used in most countries of the world, each basic unit of measure of length, area, or volume can be divided into centimeters. A meter consists of 100 centimeters, a square meter consists of 10,000 square centimeters, and a cubic meter consists of 1,000,000 cubic centimeters.

The officer in command of a Roman century, originally a troop of 100 soldiers.

In ancient Rome, a *century* was approximately equal to a company in the U.S. Army, and a centurion was roughly equivalent to a captain. Centurions play a role in the New Testament; Jesus performs a miracle for a centurion in Capernaum, centurions are present at the crucifixion, and in later years St. Paul is arrested by centurions. According to a writer of the time, centurions were chosen for their size and strength, their abilities at swordplay and at throwing missiles, and the quality of their discipline,