Intercourse, commerce, traffic, dealings, communication, communion, conversation, converse, correspondence are comparable when meaning the connection established between persons or peoples through a medium that permits interchange (as of information, of opinions, of ideas, or of goods).
Intercourse usually means little more than this and requires a qualifying adjective to indicate the things interchanged or the medium permitting interchange. In ordinary use, when employed without qualification, intercourse means social intercourse or the normal interchange of such things as ideas, opinions, news, and civilities between one person or group and another with whom there are more or less intimate relations.
Commerce, which applies primarily to the interchange of goods by buying and selling ((for this sense, see BUSINESS 3 ) also is used in the more general sense of intercourse. The word tends to be restricted in its application to intercourse, through the spirit or mind, that involves an interchange of ideas or influences without a necessary interchange of words though it is occasionally used of sexual intercourse.
Traffic (see also BUSINESS 3 ) is used chiefly when such connotations derived from its commercial senses are to be suggested as the interchange of goods, especially of tangible or material goods, or a rapid passing to and from the persons or things concerned.
Dealings usually implies a closer connection and one with more familiarity or less formality or one having for its object mutual or personal gain.
Traditionally communication is less general than any of the preceding terms because it implies intercourse based on an exchange of symbols and especially words, but communication suggests, as the preceding terms do not, mutuality and the shared background of experience that has given rise to a comprehensible set of symbols; it therefore is appropriately used of nonhuman interactions or of the process or art of effectively interchanging symbols or, in the plural, of the means by which spatially or temporally separated individuals or groups engage in such exchanges.
Communion usually implies intercourse between those who are close in love or sympathy or in mutual understanding; it often suggests rather than implies spiritual intercourse or the absence of words.
Conversation has a use, chiefly in the phrase criminal conversation, in which it is equivalent to sexual intercourse, and converse has a poetic sense in which it approaches communion. In general use, however, both terms usually imply free and often lively oral interchange of opinions, comments, or news between two or more persons; conversation often applies specifically to the act of interchanging opinions, ideas, and information in talk, and converse, to the ideas, gossip, and opinions involved in such conversation.
Correspondence implies intercourse through an interchange of letters.