# Av

**Avalanche**- A cumulative ionization process.
**Avatar**- A picture or figure representing a person in an online environment.
**Average**- A statistic calculated by summing a set of data values and dividing by the number of values.
**Average Bond Enthalpy**- Average enthalpy change per mole when the same type of bond is broken in the gas phase for many similar substances.
**Average Deviation**- The absolute value of the difference from the mean for each data value, summed, then divided by the number of values.
**Average Expected Payoff**- An estimate of the amount that will be gained in a game of chance, calculated by multiplying the probability of winning by the number of points won each time.
**Average Room Absorption Coefficient**- Total room absorption in sabins or metric sabins, divided by total room surface area in consistent units of square feet or square metres.
**Average Sound Pressure Level in a Room**- The space average sound pressure level taken over the total volume of the room.
**Average Speed**- The distance traveled divided by the time taken.
**Averaging**- In any process it is often necessary to average a number of measurements to gain
any confidence in the measured value.
**Averroes, Ibn Roshd**- Arabian philosopher and physician who helped to advance the science of his time.
**Aviation**- Lists all Aviation topics in the Encyclopaedia
**Aviation Books**- Lists all Aviation Books in the Encyclopaedia
**Aviation Calculations**- Lists all Aviation Calculations in the Encyclopaedia
**Aviation Conversions**- Lists all Aviation Conversions in the Encyclopaedia
**Aviation Weblinks**- Lists all Aviation Weblinks in the Encyclopaedia
**Avogadro, Armedeo**- His work provided a simple way to determine atomic weights and molecular weights of gases.
**Avogadro′s Law**- Equal volumes of an ideal gas contain equal numbers of molecules, if both volumes are at the same temperature and pressure.
**Avogadros Number**- N = 6.022045x10
^{23} mol^{-1}