portret

/portret/

Cases

SingularPluralWhen to use it
nominativeportretthe portraitportretlethe portraitsthe plain dictionary form — the doer of the sentence
genitiveportretnithe portrait'sportretlenithe portraits'the owner — whose it is
accusativeportretnithe portrait (as the object)portretlenithe portraits (as the object)a specific, known object — whom or what
dativeportretgeto the portraitportretlegeto the portraitsdirection or recipient — to where, to whom
locativeportretdeat / in the portraitportretledeat / in the portraitswhere it is; also having — mende bar, "I have it"
ablativeportretdenfrom the portraitportretledenfrom the portraitswhere it comes from; also "than" when comparing
When to use each case
nominative
the plain dictionary form — the doer of the sentence
genitive
the owner — whose it is
accusative
a specific, known object — whom or what
dative
direction or recipient — to where, to whom
locative
where it is; also having — mende bar, "I have it"
ablative
where it comes from; also "than" when comparing

The endings are the same ones the pronouns wear — that page explains when each case is used.

With an owner

One ownedSeveral owned
myportretimmy portraitportretlerimmy portraits
yourportretingyour portraitportretleringyour portraits
his / herportretihis / her portraitportretlerihis / her portraits
ourportretibizour portraitportretleribizour portraits
you all'sportretigizyou all's portraitportretlerigizyou all's portraits
theirportretleritheir portraitportretleritheir portraits

The overlap in the last rows is real, not a mistake: portretleri can mean "his / her portraits", "their portrait", or "their portraits" — context decides.