isomer
noun [ C ] chemistry specialized uk/ˈaɪ.sə.mər/ us/ˈaɪ.soʊ.mɚ/
（同分）异构体
any one of a group of chemical substances which all have the same number and type of atoms but in which the arrangement of the atoms is slightly different between each substance
structural/geometrical/optical isomers 结构／几何／光学同分异构体