名词
中文翻译：硬化
同义词：
['hardening', 'hardening例句：1. The oil has stiffened the metal surface.（油已经使金属表面变硬了。）2. As the material aged', 'it began to stiffen.（随着材料的老化，它开始变硬了。）']
例句：
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1. The oil has stiffened the metal surface.
油已经使金属表面变硬了。
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2. As the material aged, it began to stiffen.
随着材料的老化，它开始变硬了。
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3. The food was stiffening in the fridge.
食物在冰箱里开始变硬了。