387. (1.) By two nouns combined, one with an unchanging case ending, the
other with full inflections: as, #aquae-ductus#, _aqueduct_;
#senātūs-cōnsultum#, _decree of the senate_; #pater-familiās#, _father
of a family_; #vērī-similis#, _like the truth_; in these words, #aquae#,
#senātūs#, #familiās#, and #vērī# are genitives, and remain genitives,
while the other part of the compound is declinable.
388. (2.) By a substantive with an adjective habitually agreeing with
it, both parts being declined: as, #rēs pūblica#, _the common-weal_;
#rēs gestae#, _exploits_; #iūs iūrandum#, _oath_; #pecūniae repetundae#,
_money claim_.
389. (3.) By nouns, chiefly substantives, in the same case placed
loosely side by side and making one idea. The two words may be used:
(_a._) Copulatively: as, #ūsus-frūctus#, _use and enjoyment_;
#pactum-conventum#, _bargain and covenant_; #duo-decim#, _two and ten_,
_twelve_; or (_b._) Appositively: one word explaining the other (1045):
as, #Iuppiter#, _Jove the Father_ (94; 133); #Mārspiter#, _Mars the
Father_, for #Mārs pater#.
390. (4.) From an original combination of an oblique case with a
preposition: as, #prōcōnsul#, _proconsul_, from #prō cōnsule#, _for a
consul_; #ēgregius#, _select_, from #ē grege#, _out of the herd_;
#dēlīrus#, _astray_, _mad_, from #dē līrā#, _out of the furrow_.