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