n, pl  -tries  1  :  correspondence in size, shape, and relative position of parts on opposite sides of a dividing line or median plane or about a center or axis - see BILATERAL SYMMETRY RADIAL SYMMETRY   2  :  the property of remaining invariant under certain changes (as of orientation in space, of the sign of the electric charge, of parity, or of the direction of time flow) - used of physical phenomena and of equations describing them .
 
 
 
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