letter received; incoming letter
Refers to a letter that has been received, often used in formal or written contexts. Not a common everyday word; 手紙 (てがみ) is the general term for 'letter'.
Thank you for the letter I received the other day.
We will consider the contents of your letter.
Sino-Japanese compound of 来 (come, incoming) and 信 (letter, message). The reading is on'yomi.