In a letter, the courteous leave taking is known as-
সঠিক উত্তর
Subscription
The phrase ‘sine die means
ব্যাখ্যা:
Subscription-এ থাকে বিদায় সম্ভাষণ। তাই, এটি courteous leave taking।
যেমন, Yours affectionately.
Source: Applied English Grammar and Composition by P C Das