Citrus tree and Fruit 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.

Fruit tree and citrus tree are semantically related. In some cases you can use "Fruit tree" instead a noun phrase "Citrus tree".

Fruit tree noun - Tree bearing edible fruit.

Citrus tree and fruit tree are semantically related. Sometimes you can replace phrase "Citrus tree" with "Fruit tree", this phrases are similar.