# 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)

ampere, A, amp
1. The basic unit of electric current in the meter-kilogram-second system; equivalent to one coulomb per second.
2. A unit of electrical current or rate of flow of electrons.

One volt across one ohm of resistance causes a current flow of one ampere.

ampere-hour, ampere hour; Ah, AH
A measure of the flow of current (in amperes) over one hour when the rate of flow is one ampere; equal to 3600 coulombs (standard international unit of electric charge).

Used to measure battery capacity.

angstrom, symbol Å
A unit of length equal to one ten-billionth of a meter (10 meters or one-ten-millionth of a millimeter), used to measure the wavelengths of electromagnetic radiation.

Named for Anders Jonas Ångström (1814-1874), Swedish astrophysicist.

apothecary weights that are no longer used
Out dated or obsolete units of mass, formerly used in pharmacies:
• Twenty grains equal one scruple.
• Three scruples equal one dram.
• Eight drams equal an apothecary's ounce; oz apoth.
• Twelve such ounces equal an apothecary's pound; lb apoth.
• There are 7,000 grains in one pound avoirdupois or 0.454 kilograms.

approximate
Not precise; a measurement that is close enough to the true number to be useful.
arc
A portion of the circumference of a circle that is represented as a curved line.
are, ares
A metric unit of area, equal to 100 square meters (119.6 square yards); and 100 ares make one hectare.
area
The measurement or extent of a two-dimensional surface enclosed within a boundary: "The area of a triangle."
arithmetic
A branch of mathematics usually concerned with four operations: adding, subtracting, multiplication, and division of positive numbers.
astronomical unit, A.U. or a.u.
1. The average distance from the earth to the sun, which equals 149,597,870 kilometers or 92,955,800 miles.

For simplicity, an AU is usually rounded off to 93,000,000 miles or 149,637,000 kilometers.

2. An astronomical unit is used to describe planetary distances.

Light travels this distance in approximately 8.3 minutes.

atmosphere, standard atmosphere, atm
In physics, a unit of pressure equal to 760 torr, 1013.25 millibars, or 1.01325 x 105 newtons per square meter (the terms used here are located in this unit).

The actual pressure exerted by he atmosphere fluctuates around this value, which is assumed to be standard at sea level and zero degrees centigrade/32 degrees Fahrenheit, and is used when dealing with very high pressures.

atomic time, atomic clocks
Time as given by atomic clocks, which are regulated by natural resonance frequencies of particular atoms, and display a continuous count of seconds.
average
The sum of several quantities divided by the number of quantities.
The number of carbon atoms in twelve grams of the carbon-12 isotope.

The relative atomic mass of any element, expressed in grams, contains this number of atoms.

It is named for an Italian physicist Amedeo Avogadro (1776-1856).

avoirdupois
1. Units used to measure the mass of any substance; except precious gems and metals, and drugs.

It includes the pound, short and long tons, ounce, and dram.

2. A system of units of mass based on the pound (0.45 kilograms), which consists of 16 ounces (each of 16 drams) or 7,000 grains (each equal to 65 milligrams).

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