Sentence:  But one thing <WSD>is</WSD> for certain : There is no dissension between Mantle , the American League 's Most Valuable Player in 1956 and 1957 , and Maris , the MVP in 1960 . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)