First class and Unconsumed

First class noun - Mail that includes letters and postcards and packages sealed against inspection.

Unconsumed and first class are semantically related. In some cases you can use "Unconsumed" instead an adjective phrase "First class".

Unconsumed adjective - Not consumed.

First class and unconsumed are semantically related. Sometimes you can use "First class" instead an adjective "Unconsumed".