Sentence:  In a sense , the showdown promised by Mr. Hammarskjold 's sudden and tragic death has been avoided ; no precedents have been set as yet ; structurally , the U.N. <WSD>is</WSD> still fluid , vulnerable to the pressures that its new and enlarged membership are bringing to bear upon it . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)