Air base and Airfield

Air base noun - A base for military aircraft.

Airfield and air base are semantically related In some cases you can use "Airfield" instead a noun phrase "Air base".

Airfield noun - A place from which aircraft operate that usually has paved runways and a terminal.

Air base and airfield are semantically related in runway for aircraft topic. You can use "Air base" instead a noun "Airfield", if it concerns topics such as airplane landing area.