Ostrich and Ratite bird

Ostrich noun - Fast-running African flightless bird with two-toed feet; largest living bird.

Ratite bird and ostrich are semantically related. In some cases you can use "Ratite bird" instead a noun "Ostrich".

Ratite bird noun - Flightless birds having flat breastbones lacking a keel for attachment of flight muscles: ostriches; cassowaries; emus; moas; rheas; kiwis; elephant birds.

Ostrich and ratite bird are semantically related. Sometimes you can replace term "Ostrich" with "Ratite bird", this terms are similar.