second declension neuter nouns

arma, armorum

arms, munitions, weapons

auxilia, auxiliorum

reinforcements

auxilium, i

help, aid

bellum, i

war

castra, castrorum

camp

caelum, i

heaven, sky

concilium, i

council

consilium,i

plan, counsel

frumentum, i

grain

frumenta, frumentorum

crops

hiberna, hibernorum

winter quarters

impedimenta, impedimentorum

baggage, baggage train

imperium, i

command, power, empire

oppidum, i

town

peccatum, i

mistake, sin

periculum, i

danger

pilum, i

javelin

praemium, i

reward

praesidium, i

garrison, protection

proelium, i

battle

regnum, i

kingdom, royal power

signum, i

standard, signal, sign

telum, i

dart

vallum, i

wall, rampart