416. Some substantives, from their meaning, have no plural.

Such are: proper names: as, #Cicerō#, _Cicero_; #Rōma#, _Rome_; material

and abstract substantives: as, #oleum#, _oil_, #vīnum#, _wine_,

#iūstitia#, _justice_; and gerunds: as, #regendī#, _of guiding_. For the

occasional use of the plural, 1105-1110.