Declensions :
a-stem nouns : These nouns end in -aḥ and -am. It's the most frequent declension.

case	singular	plural	dual
nom.	putraḥ	putrāḥ	putrau
voc.	putra	=nom.	=nom.
acc.	putram	putrān	=nom.
instr.	putrena	putraiḥ	putrābhyām
dat.	putrāya	putrebhyāḥ	=instr.
abl.	putrāt	=dat.	=instr.
gen.	putrasya	putrānām	putrayoḥ
loc.	putre	putreṣu	=gen.

Nouns in -am.
They have different endings only in nom. acc. voc. .

case	singular	plural	dual
nom.acc.voc.	nagaram	nagarāni	nagare
instr.	nagarena	nagaraiḥ	nagarābhyām
dat.	nagarāya	nagarebhyāḥ	=instr.
abl.	nagarāt	=dat.	=instr.
gen.	nagarasya	nagarānām	nagarayoḥ
loc.	nagare	nagareṣu	=gen.

Nouns in -ā.

case	singular	plural	dual
nom.	senā	senāḥ	sene
voc.	sene	=nom.	=nom.
acc.	senām	=nom.	=nom.
instr.	senayā	senābhiḥ	senābhyām
dat.	senāyai	senābhyāḥ	=instr.
abl.	senāyaḥ	=dat.	=instr.
gen.	senāyaḥ	senānām	senayoḥ
loc.	senāyam	senāsu	=gen.