Sideways and Side by side

Sideways adverb - With one side faced forward.

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

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

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