Symmetry

优选词，正式主题词

1. The quality of having parts that match each other, especially in a way that is attractive, or similarity of shape or contents (Cambridge Dictionary). 2. A symmetry operation for a molecule or crystal is defined as an operation that interchanges the positions of the various atoms and results in the molecule or crystal appearing exactly the same (being in a symmetry-related position) as before the operation. (ScienceDirect, Space Groups for Solid State Scientists (Third Edition), 2013)