Wikipedia states that:
xDNA contains expanded bases, in which a benzene ring has been added, which may pair with canon bases, resulting in four possible base-pairs (8 bases:xA-T,xT-A,xC-G,xG-C, 16 bases if the unused arrangements are used). Another form of benzene added bases is yDNA, in which the base is widened by the benzene.
In this context, does widened and expanded refer to the same thing? If so, what would be the exact different between yDNA and xDNA.
NOTE: I am not referring to the X and Y chromosomes.