A balloon is an inflatable flexible bag filled with
a gas, such as helium, hydrogen, nitrous oxide,
oxygen, or air. Modern balloons can be made from
materials such as rubber, latex, polychloroprene,
or a nylon fabric, while some early balloons were
made of dried animal bladders. Some balloons are
used for decorative purposes, while others are used
for practical purposes such as meteorology, medical
treatment, military defense, or transportation...
