傍聴【ぼうちょう】
listening (to a lecture, hearing, parliament session, etc.), attending (without participating), sitting in (e.g. on a meeting), observing
傍ら【かたわら】
side, edge, beside, besides, nearby, while (doing), in addition to, at the same time
傍観【ぼうかん】
looking on, standing by and watching, sitting back and watching, remaining a spectator
傍受【ぼうじゅ】
interception, monitoring, tapping