Erstwhile and Long ago

Erstwhile adverb - At an earlier or previous time.

Long ago and erstwhile are semantically related in formerly topic. In some cases you can use "Long ago" instead the word "Erstwhile" as an adverb or an adjective.

Long ago adverb - Of the distant or comparatively distant past.

Erstwhile and long ago are semantically related in earlier topic. You can use "Erstwhile" instead the phrase "Long ago" as an adverb or an adjective, if it concerns topics such as formerly, olden, in the past, previous in time or order.