What's the difference between purlin, rafter and beam?

Purlin: It is a small beam used to cross the beam and support rafters or roof panels.

Raft: A wooden pole installed on a roof to support roofing materials.

Beam: refers to a horizontal strip-shaped load-bearing member. Wooden shelf refers to the long wood placed on the pillars in the front and back direction.

Purlin: Chinese character, pronounced lǐn, originally meant to span a small beam supporting rafters or roof slabs. Also known as "truss".

Rafter: Chinese character, pronounced chuán, which means a wooden pole installed on the roof to support the roof material.

Liang: Generally, it is used in large buildings such as big houses, mansions, halls, big Buddha halls and big ancestral halls. Moreover, the surfaces of the big moon beam and the flat beam are not bare. After the construction is completed, they must be carved or painted, and pictures such as dragons and phoenixes must be carved in royal buildings. For example, an emperor in the Qing Dynasty once wrote a couplet "Carving a beam and painting a double phoenix dance", and then the minister replied: "Painting.