Refers to a person who evaluates and selects entries in a contest, competition, or anthology. Often used in literary, artistic, or formal selection contexts.
He served as a judge for the tanka contest.
The judges' evaluations determine the winning entries.
He served as the judge for the haiku contest.
She was chosen as the judge for the literary award.
The judge selected the best entry.
選考委員 refers to a member of a formal selection committee (e.g. for awards or admissions), whereas 選者 is often a single respected individual chosen to judge a literary or artistic contest.
選手 (an athlete or player) shares the kanji 選 with 選者 but refers to a competitor, not the person who judges or selects entries.
Compound of 選 (sen, 'select') and 者 (sha, 'person'). The reading せんじゃ is a standard on'yomi combination.