Cách sử dụng
The word 'harden' means to make something tougher or more resistant. It's often used in reference to materials like metal or concrete that need to be strengthened. It can also be used in terms of emotions, like when someone toughens up emotionally after a difficult experience. For example, "The workers need to harden the steel to ensure it lasts longer," or "He had to harden his heart to say goodbye to his friend."