2.  Plurals by formation, derived chiefly from adjectives:  acoustics, aeronautics, analytics, bitters, catoptrics, commons, conics, credentials, delicates, dioptrics, economics, ethics, extraordinaries, filings, fives, freshes, glanders, gnomonics, goods, hermeneutics, hustings, hydrodynamics, hydrostatics, hydraulics, hysterics, inwards, leavings, magnetics, mathematics, measles, mechanics, mnemonics, merils, metaphysics, middlings, movables, mumps, nuptials, optics, phonics, phonetics, physics,[146] pneumatics, poetics, politics, riches, rickets, settlings, shatters, skimmings, spherics, staggers, statics, statistics, stays, strangles, sundries, sweepings, tactics, thanks, tidings, trappings, vives, vitals, wages,[147] withers, yellows.

3.  Plurals by composition:  backstairs, cocklestairs, firearms,[148] headquarters, hotcockles, spatterdashes, self-affairs.  To these may be added the Latin words, aborigines, antipodes, antes, antoeci, amphiscii, anthropophagi, antiscii, ascii, literati, fauces, regalia, and credenda, with the Italian vermicelli, and the French belles-lettres and entremets.

OBS. 29.—­There are several nouns which are set down by some writers as wanting the singular, and by others as having it.  Of this class are the following:  amends,[149] ancients, awns, bots, catacombs, chives, cloves, cresses, dogsears, downs, dregs,[150] entrails, fetters, fireworks, greens, gyves, hatches, intestines, lees,[151] lungs, malanders, mallows, moderns, oats, orts, pleiads, premises, relics, remains, shackles, shambles,[152] stilts, stairs, tares, vetches.  The fact is, that these words have, or ought to have, the singular, as often as there is any occasion to use it; and the same may, in general terms, be said of other nouns, respecting the formation of the plural.[153] For where the idea of unity or plurality comes clearly before the mind, we are very apt to shape the word accordingly, without thinking much about the authorities we can quote for it.

OBS. 30.—­In general, where both numbers exist in common use, there is some palpable oneness or individuality, to which the article a or an is applicable; the nature of the species is found entire in every individual of it; and a multiplication of the individuals gives rise to plurality in the name.  But the nature of a mass, or of an indefinite multitude taken collectively, is not found in individuals as such; nor is the name, whether singular, as gold, or plural, as ashes, so understood.  Hence, though every noun must be of one number or the other, there are many which have little or no need of both.  Thus we commonly speak of wheat, barley, or oats, collectively; and very seldom find occasion for any other forms of these words.  But chafferers at the corn-market, in spite of Cobbett,[154] will talk about wheats and barleys, meaning different kinds[155] or qualities; and a gardener, if he pleases, will tell of an oat, (as does Milton, in his Lycidas,) meaning a single seed or plant.  But, because wheat or barley generally means that sort of grain in mass, if he will mention a single kernel, he must call it a grain of wheat or a barleycorn.  And these he may readily make plural, to specify any particular number; as, five grains of wheat, or three barleycorns.