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.