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keystone noun [C] (IMPORTANT PART)
the most important part of a plan, idea, etc. on which everything else depends
keystone
noun [ C ]
UK /หkiหstษสn/ US
the most important part of a plan, idea, etc. on which everything else depends:
Selling overseas has been, and always will remain, one of the keystones of our national prosperity.
A keystone of its corporate strategy is to invest in people, technology, and training to create a brand.
https://dictionary.cambridge.org/dictionary/english/keystone
KEYSTONE
the middle stone in the top of an arch that has a special shape and holds all the other stones in position
The keystones are richly carved and the arch soffit is deeply coffered and enriched.
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