这两个短语的确经常被译为同一个术语——服务合同，但其实，这样的翻译是错误的，这两个短语的含义完全不同。

简单地说，如果你是一个单位的正式员工，你和用人单位签订的是contract of service（劳动合同，service多用单数）；如果你在业余时间做点私活（比如翻译），你与用户签订的合同则是contract for services（劳务合同，即劳动服务合同；service多用复数）。

中国法律对劳动合同和劳务合同是这样界定的：“劳务合同”是经济合同（economic contracts），是劳务方以自己的“劳务”（服务）成果为义务，并得到相应劳务报酬的合同；而“劳动合同”是以劳动关系（labor/employment relationship）为基础的合同，劳动者根据用工单位的安排和规定从事劳动，并按月领取报酬。“劳务合同”是《劳动法》（Labor Law）和《劳动合同法》（Labor Contract Law，后者是对前者的细化）的调整规范，两者适用的法律规范是不同的。

如与雇主签订的是“劳动合同”，则雇主要遵守最低工资标准和缴纳“三金”（医疗保险金、失业保险金、养老保险金）；如果与雇主签订的是“劳务合同”，就是干完规定的工作，拿钱走人，雇主什么也不管。

关于劳动合同和劳务合同的区别，国内外相同。我们可以看一些相关的英文解释：

Employment relationships can be divided into two forms - the employee and the independent contractor. The employee is hired under a contract of service and he is an independent contractor under a contract for services. The distinction between the two is not always obvious and it falls to the courts to decide on the issue of the nature of the employment relationship.

Another reason why it is important to distinguish between a contract of services and a contract for services is that the system of taxation applied to each category is quite different. In a contract of services, the employer is responsible under the PAYE system, whereas in a contract for services, the independent contractor is subject to the self-assessment system.

反过来，中文的“劳动合同”可以翻译为contract of service，“劳务合同”可以翻译为contract for services。为了保留中国特色，也可以分别翻译为labor contract和labor services contract。但为了避免混淆，最好使用contract of employment（劳动合同）和contract for services（劳务合同）。

参考书目：李长栓——《法律术语翻译二十讲》