Every profession or trade, every art, or every science has its technical vocabulary, the function of which is partly to designate things or processes which have no names in ordinary English, and partly to secure greater exactness in nomenclature (术语). Such special dialects, or jargons, are necessary in technical discussion of any kind. Being universally under stood by the devotees of the particular science or art, they have the precision of a mathematical formula. Besides, they save time, for it is much more economical to name a process than to describe it. Thousands of these technical terms are very properly included in every large dictionary, yet, as a whole, they are rather on the outskirts of the English language than actually within its borders. Different occupations, however, differ widely in the character of their special vocabularies. In trades and handicrafts and other vocations, such as farming and fishing, that have occupied a great number of men from remote times, the technical vocabulary is very old. It consists largely of native words, or of borrowed words that have worked themselves into the very fiber of our language. Hence, though highly technical in many particulars, these vocabularies are more familiar in sound, and more generally understood, than most other technicalities. The special dialects of law, medicine, divinity, and philosophy have also, in their older strata, be come pretty familiar to cultivated persons, and have contributed much to the popular vocabulary. Yet, every vocation still possesses a large body of technical terms that remain essentially foreign, even to educated speech. And the proportion has been much increased in the last fifty years, particularly in the various departments of natural and political science and in the mechanic arts. Here new terms are coined with the greatest freedom, and abandoned with indifference when they have served their turn. Most of the new coinages are confined to special discussions and seldom get into general literature or conversation. Yet, no profession is nowadays, as all professions once were, a closed guild. The lawyer, the physician, the man of science, or the priest associates freely with his fellow creatures, and does not meet them in a merely professional way. Furthermore, what is called popular science makes everybody acquainted with modem views and recent discoveries. Any important experiment, though made in a remote or provincial laboratory, is at once reported in the newspapers, and everybody is soon talking about it--as in the case of the Roentgen rays and wireless telegraphy. Thus, our common speech is always taking up new technical terms and making them commonplace.
The author's main purpose in the passage is to ______.

A. describe a phenomenon
B. argue a belief
C. propose a solution
D. stimulate action