retainer fee 是什么费？

Retainer fee是聘用费

retainer fee是法律专有用词，这个词在中国或许还没有一致的中文翻译。但在香港法律界，其中文是“聘用费”，聘用费是指预留或保留某位大律师为某宗案件或某位当事人提供服务而付予大律师的费用。

英国的法律入门书籍是这般用较为通俗的语言来描述“聘用费”的：
A retainer fee is the fee which detains an attorney for legal counsel. With this fee, the attorney is certain of the seriousness of your intentions and can take your case to heart.

聘用费都是预先支付，律师办事之后就不断从预付的金额中扣除，多退少补。但实际上是“多退”居多，没有“少补”的。

英国的所谓大律师（counsel），在香港中文叫“讼务律师”，这是要和“事务律师”（solicitor）区分开来。

retainer 根据以下解释， 应是专用于律师业
定金，预聘费
n. the advance payment to an attorney for services to be performed, intended to insure that the lawyer will represent the client and that the lawyer will be paid at least that amount. Commonly in matters which will involve extensive work there will be a retainer agreement signed by the attorney and client. Further payments for services can be expected as the time spent on the legal matter increase. Most lawyers do not want to be owed money, and wish to