1. 2nd Declension nouns
US, um and r words

2. 2nd Declension Second declension are mostly masculine and neuter nouns
We know they are 2nd declension because they have a long i in the genitive singular.
Most 2nd declension nouns end is us or um
A few end in r

3. 2nd Declension-us Nom: equus equi Gen: equi equorum Dat: equo equis
Acc: equum equos
AbL: equo equis
equus, equi, m, horse

4. 2ND DECLENSION-R NOM: puer pueri GEN: pueri puerorum DAT: puero pueris
ACC: puerum pueros
ABL: puero pueris
PUER, PUERI, M, BOY

5. 2nd Declension-um Nom bellum* bella* Gen belli bellorum
Dat bello bellis
Acc bellum* bella*
abl bello bellis
bellum, belli, n, war

6. NEUTER NOUN RULE
NEUTER NOUNS ARE ALWAYS THE SAME IN NOM AND ACC CASES!

7. And now.... to abc song Us, I, O, Um, O, I, Orum
Is, Os, Is second declension.