In depth
A subject is a person who owes allegiance to a sovereign (historically a monarch); the term persists in some Commonwealth countries as 'British subject'.
Before 1949, all people born within the British Empire were 'British subjects' regardless of where they lived. The British Nationality Act 1948 created distinct citizenships for each dominion (Canadian, Australian, etc.), with 'British subject' retained as a common status.
The 1981 British Nationality Act replaced 'British subject' with several categories: British citizen, British Overseas Territories citizen, British Overseas citizen, British subject (narrow sense), British protected person, and British National (Overseas).
Related terms
Nationality is the legal relationship between a person and a state, conferring rights and obligations; in most contexts it is synonymous with citizenship, though some countries distinguish the two.
The British Nationality Act 1981 is the principal UK citizenship law, which created the current categories of British nationality and governs citizenship by descent.
Citizenship by descent (CBD) is the legal right to acquire a country's citizenship through one's ancestors — typically a parent, grandparent, or great-grandparent — without being born in that country, based on the principle of jus sanguinis.
Jus sanguinis (Latin for 'right of blood') is the principle that grants citizenship based on the citizenship of one's parents or ancestors, regardless of where one is born.
Jus soli (Latin for 'right of the soil') grants citizenship based on being born in the territory of the state, regardless of the parents' citizenship.
Dual citizenship (also called multiple citizenship) is the status of being a citizen of two or more countries simultaneously, with the rights and obligations of each.