section of a group
A section of a group isa quotient
(http://planetmath.org/QuotientGroup) of a subgroup
of .That is, a section of is a group of the form ,where is a subgroup of , and is a normal subgroup
of .
A group is said to be involved in a group if is isomorphic to a section of .
The relation ‘is involved in’ is transitive
(http://planetmath.org/Transitive3),that is, if is involved in and is involved in ,then is involved in .
Intuitively, ‘ is involved in ’means that all of the structure of can be found inside .