# Measurements and Mathematics Terms

#### (mathematics is the deductive study of quantities, magnitudes, and shapes as determined by the use of numbers and symbols while every branch of science and engineering depends on mathematics; measurement is the process of associating numbers with physical quantities and phenomena and measurement is fundamental to the sciences; to engineering, construction, and other technical fields; and to almost all everyday activities)

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").

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.

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*.

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*.

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 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".

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

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.

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.

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