Opacity
* Opacities block light and blur images before they reach the retina
  - can occur in any area of the lens
  - develop from bleeding in diabetic retinopathy or trauma
* affects a documents readability.
* contributes to the inability of some countries to borrow in their own currencies.
* controls how transparent the lightning is.
* determines the transparency, if any, of the stamped pattern.
* is also very important, since green and purple are colors that play against each other.
* is an indicator of changes in performance of particulate control systems
  - orthogonal issue
  - improved by optimal sizing of the titanium dioxide particles
  - quality
  - related to particulate pollution
* is the inverse of transmission or reflectance
  - light stopping power of a a material
  - opposite to transparency
  - resistance of a gas to the flow or radiation
  - thus a vital quantity in any calculation of stellar structure or stellar pulsation
* measure of how visible a plume of smoke is.
* measurement of the degree to which smoke obstructs the view of objects behind it.
* measurement, on a percentage scale, of how much light is blocked by the exhaust plume.
* measures the amount of light that can penetrate smokestack emissions.
* physical phenomenon
* refers to a paper's ability to prevent print from showing through to the other side.
* refers to the appearance of the radiographic image of the patient
  - extent to which radiation is blocked by the medium it is travelling through
  - incomprehensible context in which content is presented

Online shopping
* IS the way of the future.
* comes naturally to young consumers.
* fast and easy way to buy gifts at great discounts.
* is all about speed and convenience.
* is made easy in a variety of fashions
  - simple through the internet
  - more likely to result in offline purchasing than online sales
  - subject to the same laws that apply to phone or mail order shopping
* is the business everyone is talking about
  - holy grail of just about every big online player
  - wave of the future - and the future is now
  - very similar to buying from mail order catalog
  - what s in store
* new way to find steals.

Overland travel
* is more about people than destinations.
+ Crime in Benin: Crime by country :: Benin
  * Overland travel can be dangerous. Highway bandits block the road. They then steal the car. There is very little security on the roads. The borders between countries are not strong.

Observational astrophysic
* interprets the electromagnetic radiation emitted by celestial objects.
* is like astronomy.
+ Astrophysics, Types of astrophysics
  * Observational astrophysics is like astronomy. Like astronomers, observational astrophysicists use telescopes to study the Universe, but observational astrophysicists study the physics of what they see to explain the Universe.

Overexposure
* can cause a rash, itching, redness, or sunburn
  - impaired judgment, dizziness, headache, drowsiness and even death
  - lung damage, including decreased lung function
  - symptoms of non-fibrotic lung injury and membrane irritation
  - unconsciousness, liver and kidney damage and death
  - result in silicosis, a lung disease which in severe cases can be fatal
  - severely irritate and burn the skin or eye causing permanent damage
* causes painful burns on skin - lasts for days
  - swelling of skin - lasts for days
  - severe damage to target organs
* is exposure.
* major fault in color slides.
* tends to create images which are almost all blacks and whites with no middle tones.

Ovipositor
* are structures on female insects in which they deposit eggs.
* reproductive organ and it is located between the cercus.