normal is not transitive
The phrase “normal is not transitive” can be used as a mnemonic for two statements.
The first is: “The relation ‘is a normal subgroup
of’ is not transitive
.” This means that, if , it does not follow that . See normality of subgroups is not transitive for more details.
The second is: “The relation ‘is a normal extension of’ is not transitive.” This means that, if and are normal extensions, it does not follow that is normal. See example of normal extension for more details.