Astern and Retral

Astern adverb - Near, toward, or in the stern of a ship or the tail of an aircraft.

Retral and astern are semantically related In some cases you can use "Retral" instead an adjective "Astern".

Retral adjective - Moving or directed or tending in a backward direction or contrary to a previous direction.

Astern and retral are semantically related in back topic. You can use "Astern" instead an adjective "Retral".