Spheres of influence: In the context of China, this term refers to areas where foreign powers had exclusive control over trade and economic privileges.
Boxer Rebellion: The Boxer Rebellion was a violent uprising in China against foreign influences, including the open door policy, by a secret society called the Society of Righteous and Harmonious Fists.
John Hay: John Hay was the Secretary of State under President McKinley and Roosevelt who played a significant role in formulating and promoting the open door policy towards China.