Measurements and Mathematics Terms

Unit of length of heavy rope or chain for mooring or anchoring a ship; originally the length of a ship's anchor cable or 120 fathoms (219 meters/720 feet), but now taken as one-tenth of a nautical mile (185.3 meters/608 feet).

The division of the year into months, weeks, and days and the method of ordering the years (past, present, and future).

From year one, an assumed date of the birth of Jesus, dates are calculated backwards (B.C., "before Christ" or B.C.E., "before common era") and forwards (A.D., Latin anno Domini, "in the year of the Lord", or C.E. "common era").

The period between one new Moon and the next which naturally averages 29.5 days, but the Western calendar uses, for convenience, a calendar month with a complete number of days, 30 or 31 (February has 28).

For adjustments, since there are slightly fewer than six extra hours a year left over, they are added to February as a 29th day every fourth year (leap year), century years being excepted unless they are divisible by 400; for example, 1896 was a leap year; 1900 was not.

An SI unit of luminous intensity, which replaced the old units of candle and standard candle.

It measures the brightness of a light itself rather than the amount of light falling on an object, which is called illuminance and measured in lux.

An alternate name in Britain for the U.S. hundredweight, which is equal to exactly 100 pounds (the British hundredweight is 112 pounds).

Introduced by British merchants around 1850, the name was apparently coined after the model of the quintal.

The cental has been confused with the centner (the English name for a German weight or mass unit, the zentner (equal to English hundredweight), equal to 50 kilograms or about 110.231 pounds).

The name centner should not be used for the cental.

The former name for the Celsius temperature scale.

A metric unit of length equal to one hundredth of a meter.

An instrument for measuring time precisely, originally used at sea.

It is designed to remain accurate through all conditions of temperature and pressure.

The first accurate marine chronometer, capable of an accuracy of half a minute a year, was made in 1761 by the English horologist and instrument maker John Harrison.

A continuous line or the plane bounded by such a line, in which every point of the line is equidistant from the central point lying on the plane.

A circle is commonly described by its radius, a straight line extending from the center of the circle to any point on the perimeter; and its diameter, a straight line extending from a point on the perimeter, through the center, to a point on the perimeter on the other side of the circle or it is expressed as "twice the radius".

A line or boundary that forms the perimeter of a circle; also, the circle that circumscribes a rounded body.

In engineering, a unit of entropy (the loss of energy as heat in any physical process).

It is defined as the ratio of energy to temperature above absolute zero.

A unit for measuring air pollution.

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.

A number or letter before a variable in an algebraic expression that is used as a multiplier.

An estimate of how tolerable conditions are for humans in hot climates.

It is calculated as the temperature in degrees Fahrenheit plus a quarter of the relative humidity, expressed as a percentage.

If the sum is less than 95, conditions are tolerable for those unacclimated to the tropics.

A denominator, the bottom number in a fraction, which is common to all the fractions within an equation.