Bell jar and Protective cover

Bell jar noun - A bell-shaped glass cover used to protect and display delicate objects or to cover scientific apparatus or to contain gases.

Protective cover and bell jar are semantically related. In some cases you can use "Protective cover" instead a noun phrase "Bell jar".

Protective cover noun - A covering that is intend to protect from damage or injury.

Bell jar and protective cover are semantically related. Sometimes you can replace phrase "Bell jar" with "Protective cover", this phrases are similar.