diagonal: (mathematics) a set of entries in a square matrix running diagonally either from the upper left to lower right entry or running from the upper right to lower left entry
set: (mathematics) an abstract collection of numbers or symbols
shasta daisy: hybrid garden flower derived from Chrysanthemum maximum and Chrysanthemum lacustre having large white flower heads resembling oxeye daisies; often placed in the genus Chrysanthemum