"She is not big but small."

Translation: Není velká, ale malá.

[m.aster]

I wrote "Je není velká, ale malá" and was marked wrong. Is "she" not required in this sentence?

[VladaFu]

"She" is not required. But your answer is wrong. You wrote "Je není". That is the same as "Is isn't". It is a nonsense.

[m.aster]

I see, so it should have been "Ona/on/ono neni." Thanks!

[Carjul3]

Whats the difference between neni and nejsi?

[VladaFu]

není is third person (he/she/it is not), nejsi is the second person (you are not)

[Austin162565]

why dont you need to say "she"? is it because velka and mala are gendered?

[VladaFu]

Personal pronouns in subjects are normally optional unless stressed.