1911 Encyclopædia Britannica/Reciprocity
RECIPROCITY (Lat. reciprocus, returning back the same way, alternating, probably from re back and pro forward), the condition or state of being reciprocal, i.e. where there is give and take, mutual influence or correspondence between two parties, persons or things. In a more particular sense, reciprocity is a special arrangement between two nations under which the citizens of each obtain advantages or privileges in their trading relations with the other. This meaning of reciprocity, however, bears a different interpretation in European and in American usage. In the former, reciprocity between two nations usually means little more than the extension by one to the other of most favoured nation treatment, i.e. such advantages as it extends to any third country (see Commercial Treaties).
But in the United States reciprocity is the term applied to the concessions or arrangements made between that country and another without reference to any third country. Thus in the United States there are a maximum and minimum tariff, the rates of the maximum tariff being enforced on the goods of those countries which have no reciprocity treaty with the United States, and the rates of the minimum on certain products of those countries which have by a reciprocity treaty given special advantages or concessions to certain products of the United States.