Christmas tree and Silver fir

Christmas tree noun - Medium to tall fir of western North America having a conic crown and branches in tiers; leaves smell of orange when crushed.

Silver fir and Christmas tree are semantically related. In some cases you can use "Silver fir" instead a noun phrase "Christmas tree".

Silver fir noun - Any of various true firs having leaves white or silvery white beneath.

Christmas tree and silver fir are semantically related. Sometimes you can replace phrase "Christmas tree" with "Silver fir", this phrases are similar.