Butterfly fish and Flying gurnard

Butterfly fish noun - Small usually brilliantly colored tropical marine fishes having narrow deep bodies with large broad fins; found worldwide.

Flying gurnard and butterfly fish are semantically related. In some cases you can use "Flying gurnard" instead a noun phrase "Butterfly fish".

Flying gurnard noun - Tropical fish with huge fanlike pectoral fins for underwater gliding; unrelated to searobins.

Butterfly fish and flying gurnard are semantically related. Sometimes you can replace phrase "Butterfly fish" with "Flying gurnard", this phrases are similar.