o
observatory (a building housing a telescope or scientific equipment) = वेधशाळा
obtuse angle = विशाल कोन
official = अधिकृत
opener = सलामी खेळाडू
operation (of a thing) = चालणे
opportunity = संधी
option = पर्याय
orbit = कक्षा
outer planets = बाह्य ग्रह
over = षटक