Sentence:  Colonial discourse relied heavily on such <WSD>essentialisms</WSD> wherein a race or ethnic group was first represented as possessing certain key features and then those very features were 'applied' to all members of the group. 
Meaning of the word marked with <WSD> tags:  The view that all members of certain groups of people (such as those with the same race, gender, age, or sexual orientation) have common, essential traits inherent to the defining feature of the group;  behavior or statement(s) that reflect such a view.