nilgai
Oribi
That would be the Impala.
Tsessebe (Damaliscus lunatus). East African antelope ending with opi, would be the Topi.
calf (baby antelope)
Springbok or steenbok. Also gemsbok, a local name for an oryx in southern Africa.
Nyala is an antelope species in Africa. It begins with the letter N.
dikdik
Topi or Tsessebe Tibetan antelope
Addax is an antelope species in Africa. It begins with the letter a.
impala
Impala
There isn't one (unless you were thinking of the gnu), but the nilgai is a large Indian antelope.