A letter of introduction written to introduce a person to another party (e.g., a medical referral or a business introduction).
専門医にかかるには紹介状が必要な場合が多い。
You often need a letter of referral to see a specialist.
彼は有名な教授からの紹介状を持っていた。
He had a letter of introduction from a well-known professor.
会社訪問の前に、担当者は紹介状をメールで送った。
Before visiting the company, the person in charge sent a letter of introduction by email.