Fourth-class mail and Third-class mail

Third-class mail and fourth-class mail are semantically related. In some cases you can replace phrase "Third-class mail" with "Fourth-class mail", this phrases are similar.

Third-class mail noun - Mail consisting of printed matter qualifying for reduced postal rates.

Fourth-class mail and third-class mail are semantically related. Sometimes you can replace phrase "Fourth-class mail" with "Third-class mail", this phrases are similar.