The theory of linear (active and passive) networks is investigated from a vector-space viewpoint. It is shown that any linear 

 -port 

 can be associated with a linear operator 

 and characterized through the kernel or hyperkernel of 

 . More precisely, 

 may be associated with a whole class of linear operators. Some of the corresponding matrices (that will be called "canonical") allow a unified treatment for the usual matrix descriptions of n-ports. This also provides a new derivation of the rules for the change of external variables in the description of 

 , as well as some results about the connectability of two 

 -port networks.