The term “diversity” is increasingly used in interpersonal and institutional discourse, yet the meanings assigned to this term are complicated and sometimes contradictory. “Diversity” may refer to multiple attributes—ethnoracial, economic, etc. It may also refer to multiple dimensions of the same attribute—heterogeneity, i.e., mixture, or the representation of disadvantaged groups, e.g., the share of Blacks. We analyze a new survey of Chicago area residents to explore what people mean by “diversity,” not when they define “diversity” in the abstract, but when they use it to describe real communities. First, we confirm that respondents are most likely to mention ethnoracial and economic differences when explaining the decision to describe their neighborhood as “diverse.” Then, we examine whether the decision to describe a neighborhood as diverse is predicted by that neighborhood’s objective ethnoracial or economic attributes, in terms of both heterogeneity and representation. We find that assessed diversity is predicted by both ethnoracial heterogeneity and the neighborhood share of Non-Whites. In addition, Whites associate diversity with economic equality. Overall, a neighborhood’s ethnoracial attributes better predict assessed diversity than its economic ones. Our findings challenge the notion, implicit in legal precedent and institutional discourse, that “diversity” is an apparent, agreed-upon quality.