Elements of b(y) that cannot be translated into elements of a'(y) constitute a residual second-language vector, denoted as b'(y) = (b' 1 (y), b' 2 (y), …, b' n (y)).
the similarity of candidate translation equivalent y to target word x is then defined as Note that a'(y)+b'(y) is a concatenation of a'(y) and b'(y) since they have no elements in common.