By and by and Then

By and by adverb - At or within a short time.

Then and by and by are semantically related. in event topic. In some cases you can use "Then" instead the phrase "By and by" as an adverb or an adjective, when it comes to topics like happening.

Then adverb - In addition to what has been said.

By and by and then are semantically related. Sometimes you can use "By and by" instead the word "Then" as an adverb or an adjective.