# Units Topics

**A**- The abbreviation of Ampere, the SI unit of Electric current.
**A**- The Ångström is an old unit used for measuring the wavelength of electromagnetic radiation including visible light and X-rays.
**aA**- Abbreviation of abampere.
**ab**- A prefix indicating that an electrical unit is part of the CGS absolute electromagnetic system.
**Abampere**- The CGS electromagnetic unit of current equal to 10 Amperes.
**Abcoulomb**- The CGS unit of electric charge equal to 10 Coulomb.
**Abfarad**- The CGS unit of capacitance equal to 1.0x10
^{9}Farad. **Abhenry**- The CGS unit of inductance equal to 1.0x10
^{-9}Henry. **Abmho**- The CGS unit that is the reciprocal of the ohm equal to 1.0x10
^{9}Siemens. **Abohm**- The CGS unit of electrical resistance equal to 1.0x10
^{-9}Ohms. **Absolute System of Units**- A system of units in which a small number of units are chosen as fundamental, and all other units are derived from them.
**Absolute Unit**- A unit defined in terms of fundamental quantities.
**abtesla**- The CGS unit of magnetic flux density equal to 10
^{-4}tesla. **abv**- Abbreviation of Alcohol by Volume.
**Abvolt**- The CGS unit of electromotive force equal to 1.0x10
^{-9}Volt. **abw**- Abbreviation of Alcohol by Weight.
**abwatt**- The CGS unit of power equal to 10
^{-7}watt. **abweber**- The CGS unit of magnetic flux equal to 10
^{-8}weber. Also known as the maxwell. **ac ft**- Abbreviation of acre foot, a volume one foot deep covering an area of one acre.
**Acoustic Ohm**- The unit of acoustic impedance.
**Acre**- A British unit of area, traditionally used in agriculture.
**Acre Foot**- A volume one foot deep covering an area of one acre.
**Acre Inch**- A volume one inch deep covering an area of one acre.
**Aeon**- In astronomical terms, 1,000 million years.
**Ah**- Abbreviation of ampere-hour.
**Alcohol by Volume**- A standard measure of how much alcohol is contained in an alcoholic beverage, expressed as a percentage of total volume.
**Alcohol by Weight**- A measure of how much alcohol is in a beverage, expressed as a percentage of the total beverage weight.
**amp**- The informal name for Ampere.
**Ampere**- The SI unit of Electric current.
**Ampere-Hour**- An alternative unit of electrical charge.
**AMU**- Defined as one twelfth of the mass of the most abundant isotope of carbon (
^{12}C) **Angstrom Star**- Unit used to measure the wavelength of X-rays.
**Angular Speed**- The rate of change of angle turned in radians.
**Apothecaries Ounce**- Once used as a measurement of weight for drugs and other medical substances.
**Approximate**- Lists all Approximate topics in the Encyclopaedia
**Are**- A derived SI Unit of area. 1 Are = 100m
^{2} **Area**- The derived SI unit of area is the m
^{2}. **Areal Weight**- The weight of fibre per unit area, width times length, of tape or fabric.
**at**- Abbreviation for Technical Atmosphere.
**atm**- An abbreviation of atmosphere.
**atmo-m**- Abbreviation of atmo-metre.
**atmo-metre**- Unit used in atmospheric physics to compare the "depth" or total volume of atmospheres, or components of atmospheres.
**Atomic Time Scale**- A time scale based on an atomic definition of the second.
**Atomic Unit**- A system of non-SI units used in quantum chemistry to simplify calculations and mathematical expressions.
**Attometre**- A distance of 10
^{-18}m. **Bank Cubic Metre**- Represents the contents of a cubic metre of rock in place, before it is drilled and blasted.
**bar**- A derived unit of pressure used in meteorology. 1 bar = 1x10
^{5}Pa. **Bar Litre**- Unit of energy used to measure the potential energy of gases under pressure.
**barg**- An abbreviation for bar gauge.
**Barn**- A unit of nuclear cross section, 1 Barn = 10
^{-28}m^{2}. **Barrel**- A unit of capacity in the oil industry.
**Barrel Bulk**- Commercial unit of volume equal to exactly 5 cubic feet or 0.141 584 cubic metres.
**Barrel of Oil Equivalent**- A unit of energy equal to approximately 6.1 gigajoules.
**Barye**- The CGS unit of pressure, equal to 1 dyne per square centimetre.
**Base Unit**- Base units are units that are fundamental building blocks in a system of measurement.
**Bcfe**- Abbreviation of Billion Cubic Feet of Gas Equivalent.
**BCM**- Abbreviation of Bank Cubic Metre.
**Becquerel**- The Becquerel is a unit used to measure a radioactivity. One Becquerel is that quantity of a radioactive material that will have 1 transformations in one second.
**Billion Cubic Feet of Gas Equivalent**- This is really an energy unit equal to about 1.091 petajoules (PJ).
**Blink**- A unit of time equal to 0.864 second. This unit is also called the metric second.
**Blondel**- Another name for an Apostlib.
**BMI**- Abbreviation of Body Mass Index.
**Board Foot**- A unit of lumber volume, a rectangular solid nominally 12" x 12" x 1". The equivalent of a board 1-foot square and 1 inch thick.
**Body Mass Index**- A measure of fatness used in medicine and health.
**boe**- Abbreviation of Barrel of Oil Equivalent.
**British Thermal Unit**- The amount of heat required to raise the temperature of 1 pound of water by 1° Fahrenheit.
**Btu**- Abbreviation of British Thermal Unit.
**Btu h**^{-1}- An abbreviation of British thermal units per hour, the unit of heat flow rate in the British system of units.
**C**- An abbreviation of coulomb, the quantity of charge which passes any section of a conductor in one second when a current of one ampere is flowing.
**Cable Length**- Originally the length of a ship′s anchor cable, 120 fathoms.
**cal**- An abbreviation of calorie, a unit of energy in the British system of units.
**Calendar Year**- 1 calendar year = 31.536x10
^{6}seconds **Calorie**- A unit of energy in the British system of units. Still used to define the amount of energy amount of energy contained in foods.
**Calorie per Second**- Unit of power.
**Calorific Value**- The ratio of energy to volume measured in joules per cubic metre.
**Candela**- The SI unit of luminous intensity.
**Canonical Time Unit**- For geocentric orbits, the time required by a hypothetical satellite to move one radian in a circular orbit of the earth's equatorial radius.
**cc**- Abbreviation of Cubic Centimetre.
**CCF**- An abbreviation for 100 cubic feet.
**cd**- An abbreviation of candela, the SI unit of luminous intensity.
**Celsius Temperature Scale**- The centigrade scale of temperature was defined as 0°C at the ice point of water and as 100°C at the boiling point of water (at 1 standard atmosphere).
**Centigrade**- The centigrade scale of temperature was defined as 0°C at the ice point of water and as 100°C at the boiling point of water (at 1 standard atmosphere).
**Centigrade Heat Unit**- The amount of heat necessary to raise one pound weight of water through 1° C.
**centihg**- 1 centimetre of mercury.
**Centimetre**- The centimetre is a unit of length and is one hundredth of a metre by definition.
**Centimetre Gramme Second**- A system of units in which the fundamental units are centimetre, gramme and second.
**Centimetre of Mercury**- A traditional unit of pressure equal to 1.333 22 kilopascal.
**Centimetre of Water**- A unit of pressure equal to the pressure exerted at the Earth′s surface by a water column 1 centimetre high, approximately 98.067 pascals.
**centipoise**- One hundredth of a poise, the CGS derived unit of dynamic viscosity of a fluid.
**CGS Units**- Abbreviation for centimetre-gramme-second.
**Chu**- Abbreviation of centigrade heat unit.
**Circular Mil Foot**- A unit of volume of a conductor having a cross-sectional area of 1 circular mil and a length of 1 foot.
**Civil Year**- A year as measured by the conventional calendar, equal to 365 days in most years but 366 days in a leap year.
**cm**- The centimetre is a unit of length and is one hundredth of a metre by definition.
**cmHg**- Abbreviation of Centimetre of Mercury.
**Collision Density**- The rate at which collisions are occurring per unit volume per unit time.
**Coulomb**- Defined as the quantity of charge which passes any section of a conductor in one second when a current of one ampere is flowing.
**cP**- An abbreviation of centipoise, one hundredth of a poise. The CGS derived unit of dynamic viscosity of a fluid.
**CPS**- Abbreviation of cycles per second.
**Crith**- A unit of mass sometimes used in the physics and chemistry of gases. The crith is equal to the mass of a litre of hydrogen at standard temperature and pressure, this is about 89.885 milligrams.
**Cross Sectional Area**- The area of a slice of an object.
**Cubic Centimetre**- Abbreviated as cm
^{3}or cc. **Cubic Foot**- 1 cubic foot = 0.0283168 m
^{3} **Cubic Foot per Minute**- British imperial unit of flow rate.
**Cubic Foot per Second**- British imperial unit of flow rate.
**Cubic Inch**- The cubic inch has traditionally been used in American to define the swept volume of internal combustion engines.
**Cubic Metre**- SI unit of volume.
**Cubic Yard**- 1 cubic yard = 0.764555 m
^{3} **Cubit**- Unit of length equal to 457.2x10
^{-3}m. **cufm**- Cubic foot per minute, a British imperial unit of flow rate.
**cumec**- A unit of flow rate and an abbreviation of cubic metres per second.
**cusec**- Abbreviation of cubic foot per second.
**cwt**- Abbreviation of hundredweight, this is an imperial unit of mass.
**dalton**- The atomic mass unit is sometimes called the dalton, after John Dalton.
**dB FS**- Abbreviation for decibels full scale, a unit of power as measured by a digital device.
**dbar**- Abbreviation of decibar.
**dBrn**- Symbol for decibels above reference noise, a unit measuring noise levels in telecommunications.
**dBu**- A logarithmic unit of power, similar to dB m but computed from voltage measurements.
**dBZ**- A unit of radar reflectivity used in meteorology. The unit measures the amount of energy returned to a weather radar site as a function of the amount transmitted.
**Debye**- Unit of dipole moment.
**decametre**- Abbreviated as dam, unit length equal to 10m.
**decibar**- A metric unit of pressure equal to 0.1 bar or 10 kilopascals.
**Decibel**- The human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems.
**decigram**- A metric unit of mass equal to 100 milligrams.
**decilitre**- Abbreviated as dl, unit volume equal to 10
^{-1}litre. **decimetre**- Abbreviated as dm, unit length equal to 10
^{-1}m. **Denier**- A unit used in measuring the thickness (fineness) of yarn. It is the mass in grams of 9000m of yarn.
**dg**- Abbreviation of decigram.
**Didot Point**- A unit of distance used in typography.
**Dots Per Inch**- A unit used to measure the resolution, or sharpness of an image.
**dpa**- Abbreviation of Displacements per Atom.
**Drex**- Used in the textile industry to measure the density of a single fiber of yarn.
**Drum**- Unit of volume sometimes used in the oil trade. The traditional standard drum of oil contains 55 U.S. gallons or about 208.198 litres.
**dyad**- A unit of quantity equal to 2, frequently used in cell biology and biotechnology.
**Dyne**- A force of 1 dyne acting on a mass of 1g imparts an acceleration of 1cms
^{-2}. **Earth Rate Unit**- Unit of angular velocity equal to 15° per hour.
**Electron Volt**- Unit of energy of moving particles. Given by the kinetic energy acquired by an electron losing one volt of potential.
**Eon**- In astronomical terms, 1,000 million years.
**Erg**- Unit of energy equal to 100.0x10
^{-9}J. **ERU**- Unit of angular velocity equal to 15° per hour.
**F**- An abbreviation of farad, the SI unit of capacitance.
**Fahrenheit**- On the Fahrenheit scale 0°C = 32°F and 100°C = 212°F
**Farad**- The SI unit of capacitance.
**Faraday**- Quantity of electrical charge associated with one mole of chemical charge equal to 96485.3C
**Faraday Constant**- F = 9.648456x10
^{4}Cmol^{-1} **fc**- Abbreviation of Foot Candle.
**Feet**- The plural of foot. One foot was defined as one third of the Imperial Standard yard. The abbreviation of foot is ft
**Feet per Minute**- Old imperial units of velocity, abbreviated as fpm or ft min
^{-1}. **Feet per Second Squared**- Old imperial unit of acceleration.
**Femtometre**- Abbreviated as fm, unit of distance equal to 10
^{-15}m. **Fermi**- A derived SI Unit of length equal to 10
^{-15}m **Fluid Ounce**- 20 fluid ounces = 1 pint
**Foot**- One foot was defined as one third of the Imperial Standard yard.
**Foot Candle**- A measure of light intensity on a surface being illuminated.
**Foot Pound**- Imperial unit of mechanical energy.
**Foot Poundal**- Unit of work, equal to the work done by a force of one poundal acting through a distance of one foot.
**ft**- One foot was defined as one third of the Imperial Standard yard. The abbreviation of foot is ft
**ft lb**- Abbreviation of foot pound, Imperial unit of mechanical energy.
**ft min**^{-1}- Abbreviation of Feet per Minute.
**ft**^{2}- Imperial unit of area.
**ft**^{3}- Cubic foot.
**ft**^{3}s^{-1}- Cubic foot per second.
**ft s**^{-2}- Abbreviation of Feet per Second Squared, an old imperial unit of acceleration.
**Fujita-Pearson Scale**- An empirical scale for estimating the wind speed of a tornado from the damage it causes.
**Galactic Year**- The unit of time in which the Solar System makes one revolution around the Milky Way galaxy.
**galileo**- The CGS unit of acceleration, one galileo is an acceleration of 1 centimetre per second per second.
**Gallon**- This unit of volume is defined in the British and American system of units. Note 1 UK gallon = 1.2 US gallons.
**Gallons per Minute**- Volume flow rate.
**Geographical Mile**- The length of 1 minute of arc of the equator.
**GHz**- Abbreviation of Gigahertz.
**Giga electron Volt**- One billion electron Volts.
**Gigahertz**- 10
^{9}cycles per second. **GPM**- Abbreviation of Gallons per Minute.
**gram**- The CGS unit of mass equal to 10
^{-3}kg. **gramme**- Older spelling of gram, the CGS unit of mass equal to 10
^{-3}kg. **Hartley**- A unit of information content equal to one of ten possible and equally likely values or states of anything used to store or convey information.
**Hectare**- An SI derived unit of area.
**Inches**- A secondary unit in the British system of units, now replaced by the SI system and the metre.
**Joule**- The SI unit of energy.
**kBq**- Abbreviation of kilobecquerel.
**kilo calories**- 1000 calories.
**kilo electron volts**- Abbreviated as keV, one thousand electron volts.
**kilo pounds per square inch**- A unit of pressure used in the imperial system of units.
**kilobase**- A unit of genetic information equal to the information carried by 1000 pairs of the base units in the double-helix of DNA.
**kilobecquerel**- A unit of radioactivity equal to 1000 atomic disintegrations per second.
**Kilogram**- The SI unit of mass is the kilogram.
**Kilogram Force**- Equivalent to the force exerted by 1 kilogram due to the local acceleration due to gravity.
**kilojoule**- One thousand joules.
**kilometre**- A length equal to 1000 metres.
**Kilometres Per Hour**- Unit of velocity used by most land based vehicles.
**kilorad**- Common unit of radiation dose equal to 1000 rads.
**kilowatt**- One thousand watts.
**kiloWatt hour**- Unit of energy equal to 3.6x10
^{6}J. **km**- Abbreviation of kilometre.
**krad**- Abbreviation of kilorad.
**kWh**- Abbreviation of kiloWatt hour.
**lbf ft**- An abbreviation of pound-force foot, the unit of torque in the old British system of units.
**Leap Year**- Leap years are years with 366 days, instead of the usual 365.
**Linear Foot**- Term used loosely to describe a one-foot length of any long, narrow object. Primarily used to distinguish it from a square or cubic foot.
**Litre**- A derived SI unit of volume.
**Litre Atmosphere**- A unit of work or energy used in the study of confined gases.
**lm h**- Abbreviation of lumen hour.
**Long Hundredweight**- The British hundredweight, equal to 112 pounds.
**Long Ton**- The traditional British ton, equal to 2240 pounds.
**lumen hour**- A unit of quantity of light, equal to one lumen of light flux continued for one hour.
**Lunar Day**- Another name for the tidal day, a unit of time equal to 24 hours 50 minutes used in tidal predictions.
**m**^{2}- SI unit of area.
**mAh**- Abbreviation of milliampere hour.
**Megabarrel**- One megabarrel equals 42 million U. S. gallons.
**Megahertz**- 1000000Hz.
**Megawatt**- One million watts.
**MegaWatt hours**- A unit of energy equal to 1,000,000 watts for one hour.
**Mercalli Scale**- A measure of the intensity of an earthquake. This is a subjective value that varies depending on where the earthquake is observed.
**Metre**- The metre is the SI unit of length.
**Metre Kilopond**- Metric unit of torque equal to 9.806 65 newton metres (Nm) or 7.233 01 pound feet.
**Metric Ounce**- A unit of mass, equal to 25 grams. Also known as a mounce.
**Metric Pound**- An informal name for a mass of 500 grams.
**Metric Second**- Also known as a blink.
**Metric System**- The international decimal system of weights and measures based on the metre and the kilogram.
**microampere**- One millionth of an ampere.
**microbar**- A unit of pressure equal to one millionth of a bar.
**Micrometre**- One-millionth of a metre.
**microvolt**- One millionth of a volt.
**milliampere hour**- One thousandth of an Ampere-hour, Ah.
**millibar**- A unit of pressure equal to 1000 dynes per square centimeter, or 1/1000 of a bar.
**milligal**- A unit of acceleration equal to 1/1000 of a gal, or 1/1000 centimeter per second per second.
**millimetre**- milli is the prefix representing a multiplication of 10
^{-3}and metre is the SI unit of length. **Million Cubic Feet Equivalent**- A unit used in the natural gas industry for one million cubic feet of gas equivalent (cfe).
**milliosmole**- One thousandth of an Osmole.
**Milliradian**- This is one thousandth of a radian.
**millitorr**- Unit of pressure equal to 10-3 torr.
**millivolt**- A unit of electrical potential equal to one thousandth of a volt.
**milliwatt**- Unit of power equal to 0.001 watt.
**mkp**- Abbreviation of Metre Kilopond.
**MKS System**- A system of units based on the meter, the kilogram, and the second.
**MKSA System**- A system of units based on the meter, kilogram, second, and ampere.
**MMCF**- Symbol for one million cubic feet.
**MMcfe**- Abbreviation of Million Cubic Feet Equivalent.
**Molar Flow Rate**- The number of moles per unit time moving through a process.
**mOsm**- Abbreviation of milliosmole.
**mounce**- A unit of mass, equal to 25 grams.
**mtu**- Abbreviation of Metric Ton Unit.
**mW**- Abbreviation of milliWatt.
**MWh**- Abbreviation for MegaWatt hours.
**Myrialitre**- A unit of volume of ten thousand litres.
**Myriametre**- Ten-thousand metres.
**nanoampere**- One billionth of an ampere.
**Nanometre**- Abbreviated as nm, unit of length equal to 10
^{-9}metres, and equal to 10 Å (Angstroms). **Nanosecond**- One billionth of a second, 10
^{-9}s. **nanovolt**- One billionth of a volt.
**Nautical Year**- Also known as a Tropical Year.
**Ncm**- Abbreviation of Newton Centimetre.
**Newton**- The SI unit of force.
**Newton Centimetre**- Metric unit of torque equal to 0.01 newton metre.
**Newton Metre**- The SI unit of Torque.
**nit**- Unit of luminance, equal to one candela per square meter, or 10
^{-4}stilb. **nm**- Abbreviation of nanometer as nm, unit of length equal to 10
^{-9}metres, and equal to 10 Å (Angstroms). **Nm**- Abbreviation of newton metre, the SI unit of Torque.
**Normal Litre**- A unit of mass for gases equal to the mass of 1 litre at a pressure of 1 atmosphere and at a standard temperature, often 0°C or 20°C
**ns**- Abbreviation of nanosecond, 10
^{-9}s. **Number of Gram Equivalent Weights**- The number calculated by dividing the mass of a substance (in grams) by the equivalent weight of the substance.
**okta**- Unit of proportion equal to 1/8, used in meteorology to record the fraction of the sky covered by clouds.
**Order of Magnitude**- A logarithmic unit used to compare the sizes of quantities.
**Osmole**- The osmotic pressure of a one molar solution of a substance that does not dissociate, such as sugar in water.
**Ounce Force**- A derived unit of force in the British system of units.
**Ounce per Gallon**- A traditional unit of mass concentration.
**Ounces**- A secondary unit in the British system of units. 1 ounce (oz) = 28.34952 g
**owu**- Abbreviation of Open Window Unit which is the original name given to the unit Sabin.
**ozf**- Abbreviated of Ounce of Force.
**Pa**- The SI derived unit of pressure is the pascal.
**Pace**- The distance between two successive falls of the same foot.
**Page**- Unit of information in computer science, usually equal to 256 bytes.
**Parts per Billion**- A unit of proportion equal to 10
^{-9}. Abbreviated as ppb. **Parts per Quadrillion**- A unit of proportion equal to 10
^{-15}. **Parts per Thousand**- A unit of proportion equal to 0.001 abbreviated ppth and also called per mill.
**pcf**- Abbreviation of Pound per Cubic Foot.
**Peck**- An old unit of volume.
**per annum**- A traditional unit of frequency equal to once a year.
**per Foot Run**- A unit of measure in woodworking where the only dimension of concern is the length. The width and thickness are not included in the calculation.
**per Foot Super**- A square foot of wood of any thickness.
**per mill**- Parts per Thousand
**PetaFlops**- One quadrillion (10
^{15}) floating-point operations per second. **Pflops**- One quadrillion (10
^{15}) floating-point operations per second. **Phot**- Photometric unit of illuminance or illumination equal to 1 lumen per square centimetre.
**picogram**- A mass equal to 10
^{-12}g. **picolitre**- A volume equal to 10
^{-12}l. **picometre**- A distance equal to 10
^{-12}metres. **Poise**- Named after the physicist Poiseuille this is the CGS derived unit of dynamic viscosity.
**Pound Force Foot**- The unit of torque in the old British system of units, abbreviated lbf ft.
**Pound per Cubic Foot**- Traditional unit of density.
**Pound per Cubic Inch**- Traditional unit of density.
**Pounds per Square Inch**- A British imperial unit of pressure. 1.0 psi = 6894.757 Pa
**ppb**- Abbreviation of Parts per Billion.
**ppth**- Abbreviation of Parts per Thousand.
**Pyron**- A unit of radiant intensity of electromagnetic radiation equal to 1 calorie per square centimeter per minute.
**Q unit**- A unit of heat energy equal to one quintillion (10
^{18}) Btu. **Radian per Second**- A common unit of angular velocity.
**Rebar Size**- Numerical size designations for steel reinforcing bars used to strengthen concrete.
**Reciprocal Megakelvin**- A unit used in colorimetry and photography to measure the wavelength of light, especially for selecting filters to adjust the colour temperature.
**Revolutions per Kilometre**- A unit for the number of times a tyre rotates in one kilometre of travel.
**Richter Scale**- A measure of the magnitude of an earthquake at its epicentre. Each point increase on the Richter scale is a 30 times increase in the magnitude.
**Rise Run**- For smaller angles, the ratio obtained when the change in offset between two centre lines is divided by the distance along either centerline.
**RPK**- Abbreviation of Revolutions per Kilometre.
**RSI**- A symbol for the R-value of insulation when stated in SI units.
**Saltspoon**- A unit of volume formerly used in U.S. food recipes and equal to 1/4 teaspoon.
**Shore Hardness**- A hardness measure determined by a Shore durometer.
**Short Ton**- A common name for the U.S. ton equal to 2000 pounds.
**Sidereal Year**- 1 sidereal year = 31.55815x10
^{6}seconds **Siegbahn Unit**- A unit of distance used for describing the wavelength of x-rays.
**Slinch**- Equal to 12 slugs, an old unit of mass.
**Specific Volume**- The volume of a unit mass of substance, the reciprocal of density.
**Square Feet**- Imperial unit of area.
**Square Metre**- The derived SI unit of area.
**Statampere**- The unit ofcurrent in the obsolete electrostatic system of units.
**Statcoulomb**- The unit of charge in the obsolete electrostatic system of units.
**Statfarad**- The unit of capacitance in the obsolete electrostatic system of units.
**Statvolt**- The unit of electromotive force in the obsolete electrostatic system of units.
**Statwatt**- The unit of power in the obsolete electrostatic system of units.
**tce**- Abbreviation of Tonne of Coal Equivalent.
**Tera Electron Volt**- One trillion electron Volts.
**Terahertz**- One trillion cycles per second, 10
^{12}Hz. **Thousandths of an Inch**- Often abbreviated as thou. A unit of length used by engineers.
**Threads per Inch**- The number of threads in a linear inch along the length of a threaded component.
**THz**- Abbreviation of terahertz, 10
^{12}Hz. **Tonne of Coal Equivalent**- A unit of energy equivalent to 29.308 gigajoules.
**Tons per Square Inch**- Old imperial unit of pressure, abbreviated as Tsi or tonf in
^{-2}. **Torino Number**- An arbitrary scale to express the likelihood that an asteroid or comet might collide with the Earth causing damage.
**tpi**- Abbreviation of Threads per Inch.
**Tropical Year**- 1 tropical year = 31.55693x10
^{6}seconds **Troy Ounce**- An old British unit of mass mainly used for measuring prescious metals. 1 troy ounce = 31.1035 g
**Unit of Blood**- Unit of volume for human blood and its components.
**Units Books**- Lists all Units Books in the Encyclopaedia
**Units Calculations**- Lists all Units Calculations in the Encyclopaedia
**Units Conversions**- Lists all Units Conversions in the Encyclopaedia
**Units Weblinks**- Lists all Units Weblinks in the Encyclopaedia
**UT**- Abbreviation of Universal Time.
**Viscous Force**- The force per unit volume or per unit mass arising from the action of tangential stresses in a moving viscous fluid.
**Volt**- The volt is the SI unit of electromotive force.
**Volt Amperes Reactive**- Unit used to measure reactive power in an AC electric power system.
**Volt-Ampere**- The amount of apparent power in an electrical circuit, equal to the product of voltage and current.
**Voltampere (VA)**- The product of rms voltage and rms current in an electronic circuit. It is the unit of apparent power in the International System of Units (SI).
**Volume**- There are a number of derived units of volume in the British system of units and the SI system of units.
**Watt**- The watt is the SI unit of power and is equal to 1 joule per second.
**Watt Hour**- A unit of energy equivalent to one watt of power expended for one hour of time.
**Watt Hour Meter**- A meter used to measure electrical energy.
**Watt Hours per Kilogram**- Unit of energy density.
**Weber**- The weber is the SI unit of magnetic flux.
**Winchester Gallon**- The US gallon, equivalent to 3.785411784 litres.
**Yard**- The yard was a unit of length of the British system of units.
**Yard of Ale**- A traditional Scottish measure of volume that is roughly 2.5 pints and served in a slender, yard-tall glass.
**yd**- An abbreviation of yard, a standard unit of length of the British system of units.
**Year**- 1 calendar year = 31.536x10
^{6}seconds **Yottametre**- A metric unit of distance equal to 10
^{24}metres. **Zettametre**- A metric unit of distance equal to 10
^{21}metres. **Zhubov Scale**- A scale for reporting ice coverage of polar seas.

**Subjects: ** Biology Chemistry Mechanical Engineering Physics