Measurements are used by virtually every person in the world. From a meteorologist announcing today's temperatures to an architect designing the next skyscraper to a parent recording their child’s height, these measurements are important to get right. However, the vocabulary for measurement words can get a little quirky — from measuring moles to calculating candelas — so we’re here to explain what these words mean and how to measure them.
Fahrenheit
The Fahrenheit temperature scale was first proposed in 1724 by German physicist Daniel Gabriel Fahrenheit. The unit is degrees in Fahrenheit, with a 32-degree freezing point and 212-degree boiling point for water. This system is used only by the United States and a few smaller countries.
Celsius
Celsius is essentially the world standard for temperature outside of the United States. The system was invented in 1742 by Swedish astronomer Anders Celsius, after whom it is named. It is based on 0 degrees for the freezing point and 100 degrees for the boiling point of water. The Celsius scale is sometimes referred to as the “centigrade scale” because of its 100-degree range.
Kelvin
The Kelvin scale is yet another way to measure temperature. A kelvin (symbol K) is the base unit of temperature in the International System of Units. The system was named after Glasgow University physicist Lord Kelvin (William Thomson). While Celsius and Fahrenheit scales were developed around the temperatures of water, the zero point for the Kelvin scale reflects the complete absence of thermal energy (−273.15 Celsius or −459.67 Fahrenheit).
Foot
“Foot” has been used in various contexts in ancient and modern measurements, ranging from 25 to 34 centimeters, or about the length of the average man's foot. This approximation was replaced by the standardized “meter,” the basic unit of the metric system in much of the world, but the United States still holds onto the foot as part of the United States Customary System of weights and measures. In 1959 the length was officially set at 12 inches, or exactly 30.48 centimeters.
Meter
The meter (or metre, depending on where you are) is a widely used unit of measurement for length. It comes from the Greek word metron, meaning “a measure.” The establishment of the metric system (based on the meter) came about during the French Revolution. The unit amounts were decided upon by the French Academy of Sciences and formally approved by King Louis XVI in 1791. The imperial system of measurement, including “pound,” “foot,” and “gallon,” was replaced by the metric system in most of the world by the mid 20th century.
Mole
It’s not the small, subterranean mammal, but it is a unit of measurement commonly used by scientists for the measurement of small entities such as atoms, molecules, and other particles. A “mole” (or “mol”) is the standard unit name. The term is derived from the word “molecule,” which can be traced back to the Latin word moles to describe a mass or barrier.
Candela
The candela scale is the only measurement based on human perception. It is used to measure the visual intensity of light, such as light bulbs. Centuries ago, "candle" was the unit name used to measure visible light and was based on a standard wax candle. This measurement was difficult because a standard candle varied by manufacturer and region. The "new candle" unit, called a "candela," was introduced in 1948. When purchasing a light bulb, you might notice the word “lumen” on the box. This is derived from the candela system and measures the total light in all directions from a source based on a universal level of brightness.
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