A-one and First-class

A-one adjective - Of the highest quality.

First-class and A-one are semantically related in good topic. In some cases you can use "First-class" instead an adjective phrase "A-one".

First-class adjective - Of the very best kind.

A-one and first-class are semantically related in good topic. You can use "A-one" instead an adjective phrase "First-class".