An element of a group, ring, etc. which is its own inverse, i.e. an element a for which a2 = e where e is the identity element. So the identity is always self-inverse; any reflection is self-inverse, as is a rotation through 180°.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。