Spectaculum is something to look at, a spectacle, show: quom hoc mihi optulisti tam lepidum spectaculum, Poen. 209.
The verb stems of these four nouns, with the exception of the first, could conceivably form nouns meaning instrument, or result of action, or place; but only one of them, spectaculum, has any of these meanings, and that, of place: tantus est ex omnibus spectaculis usque a Capitolio plausus excitatus est, Sest. 124.
B. Abstract -culum Words, All Denoting Action
There are four abstract -culum words, all expressing primarily action itself.
Curriculum (curro) is a running: curre in Piraeum atque unum curriculum face, Trin. 1103.
Periculum (stem seen in experire) is a trial, attempt, also danger, risk: fac semel periculum, Cist. 504; nescio quanto in periculo sumus, Phor. 58.
Saeculum (sero), if this etymology is correct, is originally a sowing, then the thing sown, a generation, race, period of time: quid mirum si se temnunt mortalia saecula, Lucr. 5, 1238; et muliebre oritur patrio de semine saeculum, Lucr. 4, 1227; saeculum spatium annorum centum vocarunt, Varro, L. L. 6, 2.
Oraculum (oro) is an utterance, usually of some god or prophet, sometimes the place where it is given: oracula ex eo ipso appellata sunt, quod inest in his deorum oratio, Top. 20, 77; exposui somnii et furoris oracula, quae carere arte dixeram, Div. 1, 32, 70; numquam illud oraculum Delphis tam celebre fuisset nisi...., Div. 1, 19, 37.
With regard, then, to the verb stems of the -culum nouns we may say that they are such as require an instrument, suggest a place, or imply the object of their action, while a few form nouns denoting action itself.
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