### density:

Air density
* can change.
* decreases with decreasing pressure and increasing temperature.
* depends on the temperature, the pressure and the humidity.
* is affected by changes in altitude and temperature
* is affected by the atmospheric pressure, temperature and humidity
  - another factor that directly influences lift
  - determined by the integral magnitude of the molecular signal return
  - greatest at the surface of the Earth
  - variable within the atmosphere
* major factor in aerodynamic performance and engine efficiency.
* makes a difference in estimates of performance and it changes from day to day.
* represents the number of atoms of nitrogen, oxygen, etc. per volume of air.

Areal density
* is the number of bits per square inch a drive can hold.
* refers to the number of bits that can be stored on a square inch of disk media.

### density:

Bone density
* Some bone density leads to osteoporosises.
* achieved in early adulthood is the major determinant of risk of osteoporotic fracture.
* appears to improve in previously heavy drinkers if they abstain.
* declines sharply during the first years of menopause.
* decreases with osteoporosis.
* depends on complex interactions between the osteoclast and osteoblast.
* has a genetic component Three distinct genetic factors contribute to fracture risk.
* is an important component in the overall health of women
  - measure used to diagnose osteoporosis
  - estimated from the characteristics of the sound waves
  - greater in blacks than in whites regardless of age
  - increased in areas of high stress and decreased in areas of low stress
  - laid down during adolescence
* is measured by calculation of the amount of gamma radiation absorbed by bone
  - with a specially designed cost-effective machine that uses ultrasonometry
  - only one aspect of the risk of fractures
  - stable for a few years and then starts to decrease
* is the amount of bone tissue in a certain volume of bone
  - biggest factor determining bone fracture risk
  - very poor, and hard to distinguish from surrounding tissue
* measurement of bone in grams per square centimeter.
* shows small increases, which are less than seen with estrogen.

### density:

Bulk density
* affects the ease with which contaminants move through the rock or soil.
* describes the soils weight to volume ratio.
* has an inverse relationship with soil structure and soil porosity.
* is highest under wheel tracks where maximum pressure is applied to the soil
  - important because it reflects the porosity of a soil
  - largely dependent on moisture content of the manure
* is the weight of a soil in a given volume
  - soil solids per unit volume of soil
  - the abrasive per unit volume, typically pounds per cubic foot

Current density
* is given by electric field at cathode.
* measure of the density of an electric current.

Drainage density
* Drainage Density Is the measure of the length of stream channel per unit area of drainage basin.
* measure of the length of channel per unit area

Energy density
* decreases asymptotically with time.
* is density
  - determined by the fat, fiber, and water content of foods
* is the amount of energy in a space divided by the volume of the space
  - number of calories in a given volume of food
  - ratio of calories to the weight of food
* measure of the energy stored in the field per unit volume of space.
* refers to the amount of energy or calories compared to the weight of the food.

High density
* High densities are observed in areas with abundant food and cover
  - correlates with semi-massive sulphides
* can produce intensified competition for resources, such as food, shelter, etc.
* is the source of strong natural character
  - urban areas while Medium and low density are rural areas

Housing density
* creates more consumers for retail businesses.
* has a significant impact on land use.