First class and Trendsetting

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

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

Trendsetting adjective - Initiating or popularizing a trend.

First class and trendsetting are semantically related. Sometimes you can use "First class" instead an adjective "Trendsetting".