English Translation
He sat down by my side.
Can 側 be がわ/かわ here, or should it be そば?
He sat down by my side.
Can 側 be がわ/かわ here, or should it be そば?
@kebukebu
そば is the only correct pronunciation in this context.
そば (spelled 側 or 傍) means “somewhere close to X).
がわ/かわ means “the direction/area/aspect/edge of X” or “side of X to support/join” (i.e. there is “the other side”).
Example sentences:
He was on my side. = He understood and supported me although there were enemies attacking me. = 彼は私側 (わたしがわ) に立ってくれた。
He was (physically) standing by my side. = He was standing somewhere within the close range of my position. = 彼は私の側 (わたしのそば) で立っていた。
The car was running on the right lane. その車は道路の右側 (みぎがわ) を走っていた。
The first sentence implicitly describes that I was trouble with someone, and he defended me. There was “the other” side but he picked up my side. “Which one” you choose is the central question of this first sentence.
The second means “to be close to me”. There is no “the other” side(s).
The third implies that there are more than one lanes of the road. And the driver picked up the right lane and dismissed the others. There is no “be close to X” meaning in this context.