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English definition of “mainstay”

mainstay

noun [C, usually singular]     /ˈmeɪnsteɪ/
the most important part of something, providing support for everything else: the mainstay of sth Antibiotic therapy is the mainstay of treatment for many infections. Cattle farming is the mainstay of the country's economy.
(Definition of mainstay noun from the Cambridge Business English Dictionary © Cambridge University Press)
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