证书，信件的英文

• letter

• 证书:    certificate; credentials
• 信件:    letter; mail; missive
• 信件:    letter; mail; missive 打印信件 a form letter; 商业信件 business letter; 发出的信件 an outgoing letter; 友好的信件 a friendly letter; 他每天有大量的信件要回复。 he has a large amount of mail to answer every day
• 证书:    certificate; credentials 结婚证书 marriage certificate; marriage lines; 毕业证书 diploma; 证书审查委员会 credentials committee
• 按信件:    by mail