What am I? I am a thing. Teachers hate me,

[keyplus90]

cow like me, monkey eats me. I am a 9 letter word. -o- - m - - y -.

[naky-nag-nat]

The answer is tautonyms, which is considered to be any word or term made from two identical parts or syllables.

The teacher hate me... because tautonyms are no longer allowed in botany

the cow like me... Bison Bison is tautonym for American Bison

Monkey eat me... Ziziphus Zizyphus is tautonym for jujube, a fruit-flavored, usually chewy candy or lozenge, liked by monkeys.

:o)

[amalgam]

Are we no longer allowed to call a wren troglodytes troglodytes?

The illustrations already given refer to biology rather than botany I would have thought ( me being pernickety as usual I'm afraid!)

[gen2]

Two more come to mind

Bufo bufo

Glis glis

[Dimbo]

No wonder the song thrush is struggling, it is turdus turdus

[dundurn]

But what has tautonyms got to do with -o--m--y-? and just to be picky as well - bison aren't cows.