Chief and First class

Chief adjective - Coming before all others in importance.

First class and chief are semantically related In some cases you can use "First class" instead an adjective "Chief".

Nearby Word: chiefly

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

Chief and first class are semantically related in prime topic. Sometimes you can use "Chief" instead an adjective phrase "First class", if it concerns topics such as best, top, most excellent, highest in importance.