Defined in these global terms, the meaning of a sign is not in general analyzable with full exactness into completely localized terms, but aspects of its meaning can be given approximate analyses, and special cases of sign relations frequently admit of more local analyses.
While it might appear that the latter two are the same, the subtle difference lies in the fact that the interpretant refers to the idea of something, and the object is the thing itself.
The representamen component of the sign can be further broken down into three categories, which are icon, index, and symbol.
An icon is slightly less abstract, and resembles to some degree the thing that it represents, and bears some physical likeness to it.
An index is the least arbitrary category of representamen, and has a definite physical tie to that which it represents.
In contradistinction to Ferdinand de Saussure's dyadic model, which assumed no material referent, Peirce's model assumes that in order for a sign to be meaningful, it must refer to something external and cannot be self-contained, as it is for Saussure.