Elegantiae terminorum

Quadragenteni, quingenteni, sexcenteni, septigenteni, octigenteni, noningenteni. Treceni, however, lacks syncope. And changed, just as viceni for vigeni and triceni for trigeni. Sexcena should be written for sexcentena. Septingentena milia seven hundred thousand is not well said for "seven times one hundred."
Dena ten each is not taken for twenty, since singuli would make ten.
Binus or bini make two each: as "there were created once two consuls," i.e., each year two consuls.
Ternus or terni make three each. Quaterni, four each. So about the others.
Poets are not used only in this singular making: as septeni among them does not make seven each, but seven each as one.
So also in the plural: as duodena astra twelve stars are twelve stars.
Also, trinus threefold is joined to both numbers.
Nouns above one hundred are syncopated; below one hundred, they are not. Adverbs, however, below one hundred are syncopated; beyond, they are not: as vicies for vigities, trities for trigities, quadragies for quadragities. So quinquagies, sexagies, septuagies, octogies, not octuagies, nonagies, not nouagies. Others are not syncopated: quinquies, sexies, septies, octies, novies, decies, centies, ducenties, tricenties, quadringenties, septingenties, octingenties, noningenties.
Dilies, bis milies, ter milies, vicies milies, and so on for others.
Septenus gurges is not "seven each," but seven each as one stream, the Nile.
Priscian explains septeno as septenario set of seven, which does not please Laurentius, since it is unheard of that any stream has a sevenfold channel. Also, these nouns indicate the number of other things that are not counted, not the multiplication of themselves: as lapis centenarius a hundred-pound stone, not that it is a hundred gems, but that it has a hundred years. Again, we do not say centenaria libra, but centuplum hundredfold.
We say "this hundred-year year," but "a hundredfold of years." We say "a septenary, a duodenary, and a centenary number."
Also, he says, "he has entered the centenary number of years," but not "a centenary year." And "he carries a millenary number in weight," but not "a millenary weight." Explain these as we are accustomed to in those numerals that signify the last of their number: decimus, undecimus, centesimus, millesimus, i.e., that which is the last of ten, eleven, one hundred, one thousand. Some also explain it thus: "he brought a hundredth fruit," that "a sixtieth," "yours a thirtieth fruit," i.e., the fruit of a centenary number, or of a sexagenary, of a tricenary, or a hundredfold, or a thirtyfold.
Numeral nouns, whether they are substantives or adjectives, can be joined in such a way that neither two substantives nor two adjectives can be alone; "two hundred, three thousand," it is said: "twice a hundred, thrice a thousand," or "two hundred."