runner; racer
General term for a person who runs in a race or competition, such as a track event or marathon.
マラソンの走者たちはスタートラインに並んだ。
The marathon runners lined up at the start line.
The batter hit with a runner on second base.
He advanced the runner to third base with a sacrifice bunt.
The runner scored on the hit, and a run came in.
The runner in the lead is approaching the finish line.
走者 refers specifically to someone running (in a race or on base), while 選手 is the broader term for any athlete or player.
打者 is the batter standing at the plate, while 走者 is a runner already on base—both are baseball roles ending in 者 but refer to different players.
走塁 is the act of running the bases, whereas 走者 is the player who is running (the runner).
The everyday counter for people: 一人 (ひとり), 二人 (ふたり), 三人 (さんにん).
More formal than 人 — used for headcounts in reservations, staff lists, and announcements (5名様).
Compound of 走 (run) and 者 (person).