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essential – adj. extremely important and necessary
orbit – v. to travel around (something, such as a planet or moon) in a curved path: to make an orbit around (something)
orbit – n. the curved path that something (such as a moon or satellite) follows as it goes around something else (such as a planet)
certain – adj. not having any doubt about something: convinced or sure
technical – adj. relating to the practical use of machines or science in industry, medicine, etc.
