| Term | Definition |
| oasis | a place where water can be found in a desert |
| observatory | a building designed for observing the stars and planets |
| Old Testament | the first part of the Christian Bible, corresponding to the Jewish Bible |
| oppression | cruel or unjust treatment |
| oracle | a person through which a god or spirit is believed to speak |
| oral traditions | the art of storytelling to record a culture's history |
| orbit | the path one heavenley body (such as a planet) follows around another (such as the sun) |
| original sin | in Christian belief, the sinful state into which all people are born |
| pagoda | a tower-shaped structure with several stories and roofs |
| painting | artwork created with paint on a flat surface such as paper or canvas |