tri = three. naux = nine.
kvar = four. dek = ten.
kvin = five. dek unu = eleven.
ses = six. dek du = twelve.

137. With the exception of "unu", none of the cardinals may receive the
plural ending "-j" or the accusative ending "-n". That is, they are
invariable in form. "Unuj" may be used to mean "some" in contrast to
"aliaj", others:

Unuj marsxis, aliaj kuris, some walked, others ran.
Mi prenis unujn kaj lasis la aliajn, I took some and left the others.

138. The preposition "el" is used after numeral adjectives expressing a
number "out of" some larger number or quantity:

Ses el la knaboj venis, six of the boys came.
Ok el tiuj libroj estas la miaj, eight of those books are mine.
El tiuj cxapeloj mi sxatas nur unu, of those hats I like only one.

[Footnote: The cardinal "unu" must not be used in the sense of the
English pronominal "one," as in "I am searching for a book, but not the
one on the table", which should be translated "Mi sercxas libron, sed ne
tiun sur la tablo."]


THE ACCUSATIVE OF MEASURE.

139. A substantive in the accusative case may be used, instead of
a prepositional phrase or an adverb, not only to express measure