How do you say letter in Chinese?
— 信 (xìn), 信件 (xìnjiàn), 書信, 书信 (shūxìn)

Generic synonyms for letter in Chinese
write寫, 写 (xiě)
Specialized synonyms for letter in Chinese
e電子郵件, 电子邮件 (diànzǐ yóujiàn), 伊妹兒, 伊妹儿 (yīmèi'er)
he(formal in all dialects) 他
sin罪 (zuì)
Terms within for letter in Chinese
address地址 (dìzhǐ)
Group relationships for letter in Chinese
alphabet字母 (zìmǔ)