In Commonwealth realm jurisdictions which use the Westminster system of government, ministers are usually required to be members of one of the houses of Parliament or legislature, and are usually from the political party that controls a majority in the lower house of the legislature. In other jurisdictions — such as Belgium, Mexico, Netherlands, Philippines — the holder of a cabinet-level post or other government official is not permitted to be a member of the legislature. Depending on the administrative arrangements in each jurisdiction, ministers are usually heads of a government department and members of the government's ministry, cabinet and perhaps of a committee of cabinet. Some ministers may be more senior than others, and some may hold the title "assistant minister" or "deputy minister". Some jurisdictions, with a large number of ministers, may designate ministers to be either in the inner or outer ministry or cabinet.
In some jurisdictions — such as Hong Kong, the Philippines, the United Kingdom, and the United States — holders of an equivalent cabinet-level post are called secretaries (e.g., the Home Secretary in the United Kingdom, Secretary of State in the United States). Some holders of a cabinet-level post may have another title, such as "Attorney-General" or "Postmaster-General".
The term minister comes from Middle English, deriving from the Old French word ministre, originally minister in Latin, meaning "servant, attendant", which itself was derived from the word 'minus' meaning "less".
In jurisdictions that use the Westminster system of government — such as the United Kingdom and Australia — ministers or their equivalents are selected from the legislature, and usually from the political party that controls a majority in the lower house of the legislature. In jurisdictions with strict separation of powers, ministers cannot be members of the legislature — such as Belgium, Mexico, Netherlands, Philippines, United States — and a legislator chosen to become a minister must resign from the legislature.