"Der Trainer hat ein Pferd und einen Elefanten."

Translation: The trainer has a horse and an elephant.

[Cristti]

Why is it "ein Pferd und einen Elefanten"? Shouldn't it be eine Elefanten? (die elefanten)

[Menschenkind]

'der/ein Elefant' (sg,) is masculine, so in this case it's 'einen Elefanten' (still sg.).

[veskojl]

No, "der Elefant" is not plural here, but rather it's declined in Akkusativ case, so it gets "-en" ending.

ein Elefant (Nom.) -- einen Elefanten (Akk.)

http://www.duden.de/rechtschreibung/Elefant

[ga2b_gar32]

on what depends the declination of the noun ?

[mizinamo]

History, I suppose.

[Skidbladner]

https://mein-deutschbuch.de/n-deklination.html

[Dalingo8]

That coach beside a horse and an elephant, also had a lion, a tiger and a bear, but the last three were constantly fighting who will be the leader of that tribe... now he only has a horse and an elephant.

[sumit.pathak]

Why "einen elefanten" and not "ein elefant"?

[mizinamo]

It's the object of hat, so you need the accusative case.

Elefant is masculine (der Elefant), so the article will be in the masculine accusative form, einen.

Elefant is a masculine weak noun / belongs to the N declension, so it takes an -en in all cases except nominative singular; thus in the accusative, it will be Elefanten.