190. Many nouns are formed from the present stems of verbs, which take
the place of roots. Stems thus used are mostly those of verbs in #-āre#
and #-īre#.
Thus, from #ōrā-#, stem of #ōrāre#, _speak_, are formed #ōrā-tor#,
_speaker_, and #ōrā-tiō#, _speech_; from #audī-#, stem of #audīre#,
_hear_, are formed #audī-tor#, _hearer_, and #audī-tiō#, _hearing_.
191. Verbs in #-ēre#, and those in #-āre# and #-īre# in which the #ā# or
#ī# is confined to the present system (868, 874) usually have parallel
nouns formed directly from a root: as,
#doc-tor#, _teacher_, #doc-umentum#, _lesson_, #doc-ilis#, _teachable_
(√#doc-#, #docēre#); #sec-tor#, _cutter_ (√#sec-#, #secāre#);
#dom-itor#, _tamer_, #dom-inus#, _master_, #dom-itus#, _tamed_ (√#dom-#,
#domāre#); #sarc-ina#, _package_ (√#sarc-#, #sarcīre#).
192. But a noun is sometimes exceptionally formed from the present stem
of a verb in #-ēre#: as, #monē-ta#, _mint_ (#monēre#); #acē-tum#,
_vinegar_ (#acēre#); #virē-tum#, _a green_ (#virēre#); #suādē-la#,
_persuasion_ (#suādēre#); #habē-na#, _rein_ (#habēre#); #egē-nus#,
_needy_ (#egēre#); #verē-cundus#, _shamefast_ (#verērī#); #valē-tūdō#,
_health_ (#valēre#).
193. Verbs in #-ere#, and particularly such as have a present in #-nō#,
#-scō#, #-tō# or #-iō# (832), usually have their parallel nouns formed
directly from a root: as,
#vic-tor#, _conqueror_ (√#vic-#, #vincere#); #incrē-mentum#, _growth_
(√#crē-#, #crēscere#); #pul-sus#, _a push_ (√#pol-#, #pellere#).
194. Sometimes, however, nouns are formed from such verb stems, and not
from roots: as, #lecti-stern-ium#, _a couch-spreading_ (#sternere#,
√#ster-#, #strā-#); #vinc-ibilis#, _conquerable_ (#vincere#, √#vīc-#);
#pāsc-uum#, _pasture_ (#pāscere#, √#pā-#); #pect-en#, _comb_ (#pectere#,
√#pec-#); #fall-āx#, _deceitful_ (#fallere#, √#fal-#).