Ltd. 是limited liability company的缩写，也简写为LLC，PLC 是publicly limited company的缩写，二者均可以表示“股份有限公司”，不同是是，前者是美国的股份有限公司，后者是英国的股份有限公司。

美国一般将公司分为closely held corporation和publicly held corporation。limited liability company是closely held corporation的一种，具体释义如下：

A limited liability company (LLC for short) is the United States-specific form of a private limited company. It is a business structure that can combine the pass-through taxation of a partnership or sole proprietorship with the limited liability of a corporation. An LLC is not a corporation under state law; it is a legal form of a company that provides limited liability to its owners in many jurisdictions. LLCs are well known for the flexibility that they provide to business owners; depending on the situation, an LLC may elect to use corporate tax rules instead of being treated as a partnership, and, under certain circumstances, LLCs may be organized as not-for-profit. In certain U.S. states (for example, Texas), businesses that provide professional services requiring a state professional license, such as legal or medical services, may not be allowed to form an LLC but may be required to form a similar entity called a professional limited liability company (PLLC).

英国一般将公司分为privately limited company和publicly limited company，publicly limited company具体释义如下：

A public limited company (legally abbreviated to PLC or plc) is a type of public company under United Kingdom company law, some Commonwealth jurisdictions, and the Republic of Ireland. It is a limited liability company whose shares may be freely sold and traded to the public (although a PLC may also be privately held, often by another PLC), with a minimum share capital of £50,000 and usually with the letters PLC after its name.[1] Similar companies in the United States are called publicly traded companies. Public limited companies will also have a separate legal identity.

我国的公司形式，基本上依据大陆法分类，在大陆法系国家，公司分为有限责任公司、股份有限公司、无限公司、两合公司和股份两合公司五种类型。而我们在翻译时，参考的是一些英汉法律词典。

比如《元照英美法词典》，只有limited company的相关释义，如下：

Limited company的对应中文是“有限公司；有限责任公司”，释义为：依公司法设立，由不超过一定人数的出资人或股东出资而组成，所有出资人或股东均以其出资额为限对公司承担责任，公司以其全部资产对公司的债务承担责任的公司形式。相对于无限责任公司，有限责任公司的出资人或股东仅就出资额为限对公司负责，对公司债权人不负直接责任；相对于股份有限公司，有限责任公司不得公开募集股份，不能发行股票，且其出资人或股东的人数有限，股权的转让也有严格限制。

所以我们在翻译时，有时也将有限责任公司译为limited company。

供参考。