Fruit tree and Pear tree

Fruit tree noun - Tree bearing edible fruit.

Pear tree and fruit tree are semantically related. In some cases you can replace phrase "Pear tree" with "Fruit tree", this phrases are similar.

Pear tree noun - Old World tree having sweet gritty-textured juicy fruit; widely cultivated in many varieties.

Fruit tree and pear tree are semantically related. You can use "Fruit tree" instead a noun phrase "Pear tree".