Trong lịch sử, nội các bắt nguồn từ phân nhóm nhỏ hơn thuộc Hội đồng Cố vấn Hoàng gia Anh. Thuật từ nội các là từ tiếng Anh "cabinet" có nghĩa là một phòng riêng tương đối nhỏ, được dùng làm nơi nghĩ ngơi hay nguyên cứu. Thuật ngữ tiếng Anh như "cabinet counsel" có nghĩa là cuộc tham vấn riêng tư dành cho nhà vua, có từ cuối thế kỷ 16 và được đánh vần không chuẩn vào thời đó nên khó mà biết được ý nghĩa của nó có phải là "council" (''hội đồng'') hay "counsel" (''cuộc tham vấn'').<ref name="OED Cabinet">''[[Oxford English Dictionary]]'': Cabinet</ref> [[Charles I của Anh]] khởi đầu "Hội đồng Nội các" chính thức trong tư cách là Hội đồng Cố vấn Hoàng gia hay "Hội đồng riêng" khi ông lên ngôi vào năm 1625.
<!-- Image with inadequate rationale removed: [[Image:20060206 cab01.jpg|thumb|right|250px|Cabinet of [[Stephen Harper]] ([[28th Canadian Ministry]])]] -->
Under the [[Westminster system]], members of the cabinet are collectively [[Responsible government|responsible]] for all government policy. All ministers, whether senior and in the cabinet or junior ministers, must publicly support the policy of the government, regardless of any private reservations. Although, in theory, all cabinet decisions are taken collectively by the cabinet, in practice many decisions are delegated to the various sub-committees of the cabinet, which report to the full cabinet on their findings and recommendations. As these recommendations have already been agreed upon by those in the cabinet who hold affected ministerial portfolios, the recommendations are usually agreed to by the full cabinet with little further discussion.
Cabinet deliberations are [[secret]] and documents dealt with in cabinet are confidential. Most of the documentation associated with cabinet deliberations will only be publicly released a considerable period after the particular cabinet disbands; for example, [[Freedom of Information Act|twenty years]] after they were discussed.
In theory the [[prime minister]] or premier is [[first among equals]]. However, the prime minister is the person from whom the [[head of state]] will ultimately take [[Advice (constitutional)|advice]] on the exercise of [[executive power]], which may include the powers to declare war, use nuclear weapons, expel ministers from the cabinet, and to determine their portfolios in a [[cabinet reshuffle]]. This position in relation to the executive power means that, in practice, the prime minister has a high degree of control over the cabinet: any spreading of responsibility for the overall direction of the government has usually been done as a matter of preference by the prime minister – either because they are unpopular with their backbenchers, or because they believe that the cabinet should collectively decide things.
The ''[[shadow cabinet]]'' consists of the leading members, or [[frontbenchers]], of an [[opposition party]], who generally hold critic portfolios "shadowing" cabinet ministers, questioning their decisions and proposing policy alternatives.
The Westminster cabinet system is the foundation of cabinets as they are known at the federal and provincial ( or state) jurisdictions of [[ Australia]], [[Bangladesh]], [[Canada]], [[Pakistan]], [[ India]], [[ South Africa]], [[ New Zealand]], and other [[ Commonwealth of Nations]] countries whose parliamentary model is closely based on that of the United Kingdom.
== United States Cabinet ==