First-class and Special delivery

First-class adjective - Of the very best kind.

Special delivery and first-class are semantically related In some cases you can use "Special delivery" instead a noun phrase "First-class".

Special delivery noun - Mail that is delivered by a special carrier (for an additional charge).

First-class and special delivery are semantically related in express mail topic. You can use "First-class" instead a noun phrase "Special delivery".