Englishfor English speakers
surgery
Noun
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Surgery is a way of removing, repairing or replacing a part of a body that involves incisions.
After the doctor performed surgery, John was able to walk again.
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Surgery can also be the place where surgery is done.
Take the patient into surgery.
theory
Noun
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A theory is an idea that tries to explain an observation.
The new information showed that his theory about growth was incorrect.
Nobody has disproved Einstein's theory of general relativity.