Rag paper and Wood pulp

Rag paper noun - Paper made partly or wholly from rags.

Wood pulp and rag paper are semantically related In some cases you can replace phrase "Wood pulp" with "Rag paper", this phrases are similar.

Wood pulp noun - Wood that has been ground to a pulp; used in making cellulose products (as rayon or paper).

Rag paper and wood pulp are semantically related in ground material from wood topic. You can use "Rag paper" instead a noun phrase "Wood pulp".