metamorphosis
meta·mor·pho·sis /ˌmɛtəˈmoɚfəsəs/ noun, pl -pho·ses /-fəˌsiːz/
1 : a major change in the appearance or character of someone or something
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• We have watched her metamorphosis from a shy schoolgirl into a self-confident businesswoman.
• a company that has gone through a series of metamorphoses
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• The government has undergone political metamorphosis since his election.
2 biology : a major change in the form or structure of some animals or insects that happens as the animal or insect becomes an adult
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• the metamorphosis of tadpoles into frogs
• The class learned about how caterpillars undergo metamorphosis to become butterflies.
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• caterpillars undergoing metamorphoses