Headmost and Number one

Headmost adjective - Coming before all others in time or order.

Number one and headmost are semantically related. in order topic. In some cases you can use "Number one" instead an adjective "Headmost", when it comes to topics like chief, earliest in order.

Number one adjective - Coming before all others in importance.

Headmost and number one are semantically related. Sometimes you can use "Headmost" instead an adjective phrase "Number one".