1A senior — someone who joined a school or workplace earlier than oneself; often used with a sense of respect toward someone older or more experienced.
田中さんは会社の先輩で、いつも親切に仕事を教えてくれる。
Mr. Tanaka is my senior at the company and always kindly teaches me about the work.
部活の先輩に相談したら、いいアドバイスをもらった。
When I consulted a senior member of my club, I got some good advice.
文化祭の準備は先輩たちが中心になって進めた。
The seniors took the lead in preparing for the school festival.
日本の職場では先輩後輩の関係が重視されることが多い。
In Japanese workplaces, senior-junior relationships are often considered important.