高空 gāokōng high altitude
How to remember 高空: 高 high + 空 empty = high altitude.
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How it is used
- High altitude / high up in the air - 高空作业 (gāokōng zuòyè) working at height, 高空坠物 (gāokōng zhuìwù) objects falling from a height.
- The airspace or elevation high above ground; a safety-relevant term.
- Register: aviation, construction, safety.