Sentence:  As towns continue to grow, replanting vegetation has become a <WSD>form</WSD> of urban utopia and green roofs are spreading fast. Last year 1m square metres of plant-covered roofing was built in France, as much as in the US, and 10 times more than in Germany, the pioneer in this field. 
Meaning of the word marked with <WSD> tags:  The shape or visible structure of a thing or person.