sidelines
n. C / Un. the area just outside the lines of a sports field where players and coaches stand. It also means a position where you watch something happen instead of being involved yourself.
n. the area immediately flanking the field of play in various sports; figuratively, a position of observation rather than active participation. Often used in the plural form to describe a state of exclusion or withdrawal from an activity.
The coach stands on the sidelines and shouts instructions to the team.
After the injury, the star player had to watch the championship game from the sidelines.
While the two major powers engaged in a trade war, smaller nations remained on the sidelines, wary of the economic fallout of choosing a side.
Commonly used in the plural form 'sidelines'. The prepositional phrase 'on the sidelines' is the standard way to describe being an observer.
standing in the sidelinesstanding on the sidelinesEnglish speakers use the preposition 'on' because the sidelines are treated as a boundary line or a flat surface.