By-and-by and Early

By-and-by noun - Time that is to come.

Early and by-and-by are semantically related. In some cases you can use "Early" instead an adverb phrase "By-and-by".

Early adverb - Before the usual or expected time.

By-and-by and early are semantically related. Sometimes you can replace phrase "By-and-by" with "Early", this terms are similar.