167. A compound word whose first element modifies the second in an
adjectival or adverbial relation is called a "descriptive compound".
The final "-a" or "-e" of the first element may be omitted, unless the
resulting combination would be ambiguous or harsh-sounding.
a. When the first element is adverbial (an adverb or preposition), the
second element may be either an adverb or adjective:
multekosta, expensive.
duonkolere, half angrily.
nevidebla, invisible.
nevole, involuntarily.
rugxflava (rugxeflava), reddish yellow.
survoje, on the way, en route.
antauxhieraux, day before yesterday.
postmorgaux, day after tomorrow.
b. An adjective may be used for the first element, if the second is an
adverb or adjective "derived from a noun-root":
samtempa, contemporaneous.
unufoje, once, one time.
trifoje, thrice, three times.
unutaga, one day's, of one day.
unuataga, the first day's.
frutempe, at an early time.
c. A noun may be used for the second element, if the resulting word
has not merely unity of form, but also unity of meaning with a
slightly different sense from that expressed by the noun and adjective
uncombined:
[Footnote: In national languages a change of accent often accompanies
such change in meaning, as "BLACKberry" (not "black BERry"), "BLUEbird"
(not "blue BIRD"), "SWEETheart" (not "sweet HEART"), German "JUNGfrau",
"virgin" (not "jung FRAU", young woman), etc.]
bonveno, a welcome (not "bona veno", a good coming).
libertempo, a vacation, leisure (not "libera tempo", free time).
superjaro, leap-year (not "super jaro", above a year).
bondeziroj, good wishes, felicitations
(not "bonaj deziroj", good desires).
plimulto, a majority (adverb and noun combined).