Sentence:  The motifs of impersonal interdependence and insulation of residential communities have polarized ; the schism between central city and suburb , Negro and White , blue collar and white collar can be viewed as symptomatic of this deeper polarization of trends in the <WSD>metropolis</WSD> . 
Meaning of the word marked with <WSD> tags:  a large and densely populated urban area; may include several independent administrative districts