A standard measurement of magnitude or quantity; The standard unit of inches is used to measure length in the U.S. Conventional System, and centimeters and meters are used in most of the other countries.

The average distance from the planet Earth to the Sun, which equals 149,597,870 kilometers or 92,955,800 miles: For simplicity, an astronomical unit is usually rounded off to 93,000,000 miles or 149,637,000 kilometers.

An astronomical unit is used to describe planetary distances.

Light travels this distance in approximately 8.3 minutes.

Units which explain the various aspects of biometrics unit.

An imperial unit of heat, now replaced in the SI system by the joule: One British thermal unit is approximately 1,055 joules).

Burning one cubic foot of natural gas releases about 1,000 Btu of heat.

A unit for measuring air pollution: A cleanliness unit can indicate the number of particles greater ghan 0.5 micrometers in diameter per cubic foot of air.

Normally, the measure is the weight of contaminants per cubic meter of air.

1. The amp, short for ampere, is the amount of electric current flowing in a wire.

The electric current is measured in electrons per second.

2. The ohm is a measure of resistance to current.

The higher the resistance at a given voltage, the less current flows. Higher resistance can be obtained by using thinner wires or by using materials which are less efficient conductors.

3. The volt is a measure of the potential energy of the source or the "pressure" pushing electrons through the wire.
4. A watt is a unit of electric power or the speed at which an electric current can function.

Electric energy is expressed in units called watt-hours, which is what is usually referred to in everyday speech when someone says "watts".

A 100-watt light bulb, that operates for one hour, uses one watt-hour and electricity which is used in a home is normally metered in kilowatt-hours, or thousands of watt-hours.

All systems of weights and measures, metric and non-metric, are linked through a network of international agreements supporting the International System of Units.

The International System is called the SI, using the first two initials of its French name Système International d'Unités.

The primary agreement is the "Treaty of the Meter" or the Convention du Mètre, signed in Paris on May 20, 1875.

Forty-eight nations have signed the treaty, including all the major industrialized countries. The United States is a charter member of the metric club, having signed the original document back in 1875.

Each SI unit is represented by a symbol, not an abbreviation. The use of unit symbols is regulated by precise rules.

These symbols are the same in every language of the world; however, the names of the units themselves vary in spelling according to national procedures; therefore, it is correct for Americans to write meter and Germans to write Meter, and it is also correct for the British to write metre, Italians to write metro, and Poles to write metr.

There is no official spelling of the SI units; however, the SI does provide the names, the definitions, and the symbols of the units which must be followed even when the spellings are different as shown below.

The fundamental SI unit of length has numerous spellings

• meter (American English, Danish, Dutch, German, Hungarian, Norwegian, Slovak, and Swedish)
• metr (Czech, Polish, Russian, Ukrainian)
• metras (Lithuanian)
• metre (British, Australian, Canadian and New Zealand English; French)
• metri (Finnish)
• metro (Basque, Italian, Portuguese, Spanish)

A list of elements associated with the International System of Units (SI)

• ampere (unit of measurement)
• are (unit of area measurement)
• atomic second
• candela (cd) (SI unit of measurement)
• centimeter (cm) (unit of measurement)
• coulomb (unit of energy measurement)
• farad (unit of measurement)
• gram (gm or g) (measurement)
• hectare (unit of measurement)
• henry (unit of energy measurement)
• hertz (unit of measurement)
• joule (unit of energy measurement)
• kelvin (K) (unit of measurement)
• kilogram (kg) (unit of measurement)
• kilometer (km) (unit of measurement)
• liter (l) (unit of measurement)
• lumen (unit of energy measurement)
• lux (unit of energy measurement)
• megohm (electronics)
• meter (m) (measurement)
• metric ton (unit of weight)
• micrometer (unit of measurement)
• millimeter (mm) (unit of measurement)
• mole (chemistry)
• nanometer (unit of measurement)
• nanotesla (physics)
• newton (unit of measurement)
• ohm (unit of energy measurement)
• pascal (Pa ) (unit of energy measurement)
• second (unit of time)
• siemens (S) (unit of energy measurement)
• tesla (unit of energy measurement)
• unit (measurement)
• volt (unit of measurement)
• watt (unit of measurement)
• weber (unit of measurement)