礁石 jiāoshí reef
How to remember 礁石: 礁 jetty + 石 stone = reef.
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How it is used
- A reef / submerged or exposed rock in the sea - 船触礁石沉没了 (chuán chù jiāoshí chénmò le) the ship struck a reef and sank.
- A concrete geography noun; often paired with 触 (chù, strike). A hazard to boats.