Citrus tree and Mandarin orange tree

Citrus tree noun - Any of numerous tropical usually thorny evergreen trees of the genus Citrus having leathery evergreen leaves and widely cultivated for their juicy edible fruits having leathery aromatic rinds.

Mandarin orange tree and citrus tree are semantically related. In some cases you can replace phrase "Mandarin orange tree" with "Citrus tree", this phrases are similar.

Mandarin orange tree noun - Shrub or small tree having flattened globose fruit with very sweet aromatic pulp and thin yellow-orange to flame-orange rind that is loose and easily removed; native to southeastern Asia.

Citrus tree and mandarin orange tree are semantically related. You can use "Citrus tree" instead a noun phrase "Mandarin orange tree".