Onychophagia is the habit that occurs compulsively in a person who...
Op art is a trend developed from the kinetic art that...
The occipital lobe is one of the smaller lobes located at the back of the...
The oligarchy is a form of government in which power is exercised by a...
The oceanic ridge is an extensive underwater mountain range formed by the...
The observable universe is everything that we can observe...
The Ottoman Empire represents one of the largest imperial...
Also known as Hunter, the Orion constellation is the largest...
Orogeny is the formation and renewal of mountains and mountain...
Overpopulation is the state in which the human population increases in...