jerk

/dʒerk/

Cases

SingularPluralWhen to use it
nominativejerkthe alderjerklethe aldersthe plain dictionary form — the doer of the sentence
genitivejerknithe alder'sjerklenithe alders'the owner — whose it is
accusativejerknithe alder (as the object)jerklenithe alders (as the object)a specific, known object — whom or what
dativejerkgeto the alderjerklegeto the aldersdirection or recipient — to where, to whom
locativejerkdeat / in the alderjerkledeat / in the alderswhere it is; also having — mende bar, "I have it"
ablativejerkdenfrom the alderjerkledenfrom the alderswhere 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
myjerkimmy alderjerklerimmy alders
yourjerkingyour alderjerkleringyour alders
his / herjerkihis / her alderjerklerihis / her alders
ourjerkibizour alderjerkleribizour alders
you all'sjerkigizyou all's alderjerklerigizyou all's alders
theirjerkleritheir alderjerkleritheir alders

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