boy

/ boj /

Cases

SingularPluralWhen to use it
nominative boy the height boyla the heights the plain dictionary form — the doer of the sentence
genitive boynu the height's boylanı the heights' the owner — whose it is
accusative boynu the height (as the object) boylanı the heights (as the object) a specific, known object — whom or what
dative boyğa to the height boylağa to the heights direction or recipient — to where, to whom
locative boyda at / in the height boylada at / in the heights where it is; also having — mende bar, "I have it"
ablative boydan from the height boyladan from the heights 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
my boyum my height boylarım my heights
your boyuŋ your height boylarıŋ your heights
his / her boyu his / her height boyları his / her heights
our boyubuz our height boylarıbız our heights
you all's boyuğuz you all's height boylarığız you all's heights
their boyları their height boyları their heights

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