• 選手せんしゅ — athlete / player
• 選択せんたく — selection / choice
• 選挙せんきょ — election
• 当選とうせん — being elected
• 再選さいせん — re-election
• 選定せんてい — screening / selection

選 combines the 辶 (movement) radical with 巽 (phonetic/meaning component). Together they convey the sense of moving toward a direction or picking a path, which developed into the meaning of “choosing” or “selecting.” It appears widely in contexts of elections, options, and decisions.

好きすきな 本ほんを 選えらんでください。
Please choose your favorite book.

彼かれは 市長しちょうに 選出せんしゅつされました。
He was elected as mayor.