1.  Of nouns in a, saliva, spittle, and scoria, dross, have no occasion for the plural; lamina, a thin plate, makes laminae; macula, a spot, maculae; minutia, a little thing, minutiae; nebula, a mist, nebulae; siliqua, a pod, siliqiuae. Dogma makes dogmas or dogmata; exanthema, exanthemas or exanthemata; miasm or miasma, miasms or miasmata; stigma, stigmas or stigmata.

2.  Of nouns in um, some have no need of the plural; as, bdellium, decorum, elysium, equilibrium, guaiacum, laudanum, odium, opium, petroleum, serum, viaticum.  Some form it regularly; as, asylums, compendiums, craniums, emporiums, encomiums, forums, frustums, lustrums, mausoleums, museums, pendulums, nostrums, rostrums, residuums, vacuums.  Others take either the English or the Latin plural; as, desideratums or desiderata, mediums or media, menstruums or menstrua, memorandums or memoranda, spectrums or spectra, speculums or specula, stratums or strata, succedaneums or succedanea, trapeziums or trapezia, vinculums or vincula.  A few seem to have the Latin plural only:  as, arcanum, arcana; datum, data; effluvium, effluvia; erratum, errata; scholium, scholia.

3.  Of nouns in us, a few have no plural; as, asparagus, calamus, mucus.  Some have only the Latin plural, which usually changes us to i; as, alumnus, alumni; androgynus, androgyni; calculus, calculi; dracunculus, dracunculi; echinus, echini; magus, magi.  But such as have properly become English words, may form the plural regularly in es; as, chorus, choruses:  so, apparatus, bolus, callus, circus, fetus, focus, fucus, fungus, hiatus, ignoramus, impetus, incubus, isthmus, nautilus, nucleus, prospectus, rebus, sinus, surplus.  Five of these make the Latin plural like the singular; but the mere English scholar has no occasion to be told which they are. Radius makes the plural radii or radiuses. Genius has genii, for imaginary spirits, and geniuses, for men of wit. Genus, a sort, becomes genera in Latin, and genuses in English. Denarius makes, in the plural, denarii or denariuses.

4.  Of nouns in is, some are regular; as, trellis, trellises:  so, annolis, butteris, caddis, dervis, iris, marquis, metropolis, portcullis, proboscis.  Some seem to have no need of the plural; as, ambergris, aqua-fortis, arthritis, brewis, crasis, elephantiasis, genesis, orris, siriasis, tennis.  But most nouns of this ending follow the Greek or Latin form, which simply changes is to _=es_:  as, amanuensis, amanuenses; analysis, analyses; antithesis, antitheses; axis, axes; basis, bases; crisis, crises; diaeresis, diaereses; diesis,