First class and Primary

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

Primary and first class are semantically related. in best topic. In some cases you can use "Primary" instead an adjective phrase "First class", when it comes to topics like better, top, highest in importance.

Primary adjective - Coming before all others in importance.

First class and primary are semantically related. Sometimes you can replace phrase "First class" with "Primary", this terms are similar.

Nearby Words: prime, prim, primarily, primal