Aro = a collection, and ero = an item; therefore aro da eroj might be termed "a collection of items."
(a). -AR- denotes a reunion or a collection of the idea contained in the root; a whole formed from a union of the parts.
Examples.—Vorto = a word, vortaro = a collection of words, a dictionary. Homo = a man, homaro = mankind. Arbo = a tree, arbaro = a wood, arbareto = a small wood, clump of trees. Arbeto = shrub, small tree, arbetaro = shrubbery, a grove. Insulo = an island, insularo = an archipelago. Vagono = a (railway) carriage, vagonaro = a train. Sekvanto = a follower, sekvantaro = suite, cortège, retinue. Nomo = a name, nomaro = list of names, a register. Ŝtupo = a step, ŝtuparo = a staircase, ŝtupetaro = a ladder, succession of small steps. Aristokrato = an aristocrat, aristokrataro = (the) aristocracy. Aro = a collection, a flock, a herd. If we wish to specify the animals, we can add the suffix to the name, as:—Bruto = cattle, brutaro = a herd of cattle. Ŝafo = a sheep, ŝafaro = a flock of sheep. Abelo = a bee, abelaro = a swarm of bees.
(b). -ER- denotes one of many objects of the same kind, a small fragment, one of many similar parts which together form the whole.
Examples.—Sablo = sand, sablero = a grain of sand. Hajlo = hail, hajlero = a hailstone. Fajro = fire, fajrero = a spark. Mono = money, monero = a coin. Polvo = dust, polvero = an atom or speck of dust. Pulvo = gunpowder, pulvero = a grain of gunpowder. Sukero = sugar, sukerero = a grain of sugar.
274. Suffixes -ĈJ- and -NJ-. (Ex. [23].)
(a). -ĈJ- is an affectionate diminutive to the Christian name of a man. It is placed after any letter of the name not later than the fifth (occasionally, the sixth).
Examples.—Vilhelmo = William, Vilhelĉjo = Willie, Vilheĉjo = Will, Vilĉjo = Billy, Viĉjo = Bill. Petro = Peter, Peĉjo = Pete. Johano = John, Johanĉjo = Johnnie, Joĉjo = Jack. Nikolao = Nicholas, Nikolĉjo = Nickie, Nikoĉjo, Nikĉjo, or Niĉjo = Nick. Ernesto = Ernest, Erneĉjo, Ernĉjo, or Erĉjo = Ernie. Patro = father, patreto, paĉjo = papa.
(b). -NJ- is a similar diminutive for a female Christian name.
Examples.—Mario = Mary, Marinjo = Molly, Manjo = Polly. Klaro = Clara, Klanjo = Clarrie. Sofio = Sophia, Sonjo = Sophy. Patrineto, patrinjo, panjo = mamma, mammy, ma.