Side by side and Sideways

Side by side adjective - Nearest in space or position; immediately adjoining without intervening space.

Sideways and side by side are semantically related In some cases you can use "Sideways" instead the phrase "Side by side" as an adjective or an adverb.

Sideways adverb - With one side faced forward.

Side by side and sideways are semantically related in exteriority topic. Sometimes you can use "Side by side" instead an adverb "Sideways".