Sentence:  The field , then , is ripe for new Southerners to step to the fore and write of this twentieth-century phenomenon , the Southern Yankeefication : the new urban economy , the city-dweller , the pains of transition , the labor problems ; the list <WSD>is</WSD> , obviously , endless . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)