  We introduce the concept of {\it self-referential order} which provides a way
to quantify structural organization in non crystalline materials. The key idea
consists in the observation that, in a disordered system, where there is no
ideal, reference, template structure, each sub-portion of the whole structure
can be taken as reference for the rest and the system can be described in terms
of its parts in a self-referential way. Some of the parts carry larger
information about the rest of the structure and they are identified as {\it
motifs}. We discuss how this method can efficiently reduce the amount of
information required to describe a complex disordered structure by encoding it
in a set of motifs and {\it matching rules}. We propose an
information-theoretic approach to define a {\it
self-referential-order-parameter} and we show that, by means of entropic
measures, such a parameter can be quantified explicitly. A proof of concept
application to equal disk packing is presented and discussed.
