The latter of these usages is the more common, and more agreeable to analogy. The same observation is applicable to the terms politics, optics, pneumatics, and other similar names of sciences.
“But in order to prove more fully that politics admit of general truths.”—Hume.
Here the term is used as plural.
Folk and folks are used indiscriminately; but the plural termination is here superfluous, the word folk implying plurality.
Means is used both as a singular and plural noun. Lowth recommends the latter usage only, and admits mean as the singular of means. But notwithstanding the authority of Hooker, Sidney, and Shakspeare, for the expressions this mean, that mean, &c., and the recommendation they receive from analogy, custom has so long decided in favour of means, repudiating the singular termination, that it may seem, perhaps, idle, as well as fastidious, to propose its dismission.
It is likewise observable, that the singular form of this noun is not to be found in our version of the Bible; a circumstance which clearly shows, that the translators preferred the plural termination.
That the noun means has been used as a substantive singular by some of our best writers, it would be easy to prove by numberless examples. Let a few suffice.
“By this means it became every man’s interest, as well as his duty, to prevent all crimes.”—Temple, vol. iii. p. 133.
“And by this means I should not doubt.”—Wilkins’s real Character.
“He by that means preserves his superiority.”—Addison.