A sign is anything, A, in a relation, r, to something, B, its object, this relation, r, consisting in fitness to determine something so as to produce something, C, the interpretant of the sign, which shall be in the relation r to B, or at least in some analogous relation. Thus, the sign involves the idea of a possible endless series of interpretations. In what relation this entire series, taken as a whole, stands to the object, B, depends upon circumstances.
This quote has been taken from Kenneth Laine Ketner's 1983 reconstruction of Peirce's 'Autobiography'
http://www.commens.org/dictionary/entry/quote-brief-intellectual-autobiography-charles-sanders-peirce-20