  The sign relation is the special species of the representing relation that obtains whenever the first interpretant (and consequently each member of the whole infinite sequence of interpretants) has a status that is mental, i.e. (roughly) is a cognition of a mind. In any instance of the sign relation an object is signified by a sign to a mind. One of Peirce’s central tasks was that of analyzing all possible kinds of signs. For this purpose he introduced various distinction among signs, and discussed various ways of classifying them.