selen

/selen/

Cases

SingularPluralWhen to use it
nominativeselenthe seleniumselenlethe seleniumsthe plain dictionary form — the doer of the sentence
genitiveselennithe selenium'sselenlenithe seleniums'the owner — whose it is
accusativeselennithe selenium (as the object)selenlenithe seleniums (as the object)a specific, known object — whom or what
dativeselengeto the seleniumselenlegeto the seleniumsdirection or recipient — to where, to whom
locativeselendeat / in the seleniumselenledeat / in the seleniumswhere it is; also having — mende bar, "I have it"
ablativeselendenfrom the seleniumselenledenfrom the seleniumswhere 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
myselenimmy seleniumselenlerimmy seleniums
yourseleningyour seleniumselenleringyour seleniums
his / herselenihis / her seleniumselenlerihis / her seleniums
ourselenibizour seleniumselenleribizour seleniums
you all'sselenigizyou all's seleniumselenlerigizyou all's seleniums
theirselenleritheir seleniumselenleritheir seleniums

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