证明书种类很多，有工作经历证明、工作经验证明、病情证明、留学生经济担保书、学业成绩证明书等等，是用来证明一个人的身份、学历、婚姻状况、身体情况等或某一件事情的真实情况。证明信的写法通常也采用一般信件格式，但多省掉收信人的姓名、地址和结束用语。称呼多用“to whom it may concern”意即“有关负责人”，但此项也可省略。写证明书要求言简意赅。　　
医生证明书

　　doctor‘s certificate
　　
　　june. 18, 2000
　　
this is to certify that the patient, mr. tomas, male, aged 41, was admitted into our hospital on june. 9, 2000, for suffering from acute appendicitis. after immediate operation and ten days of treatment, he has got complete recovery and will be discharged on june. 19, 2000. it is suggested that he rest for one week at home before resuming his work.
　　
　　jack hopkins

　　surgeon-in-charge
　　
　　医生证明书
　　
　　2000年6月18日
　　
兹证明病人托马斯先生，男，41岁，因患急性阑尾炎，于2000年6月9日住院。经立即施行手术和十天治疗后，现已痊愈，将于2000年6月19日出院。建议在家休息一个星期后再上班工作。　　
　　
　　主治医生：杰克·霍普金斯　　
　　
　　公证书

　　certificate
　　
　　(90)lu zi, no. 1130
　　
this is to certificate that mr. zhao qiangwen holds a diploma issued to him in july, 1980 by shandong university (diploma no. 064)and that we have carefully checked the seal of the university and the signature by president zhou yong sen.