Usurpation is the act of taking power, a position, a title, or a right that is not yours to take — taking it by force, by trickery, or just by walking in and acting as if it were already yours. The word is a noun; the verb is 'usurp'. It is a formal, bookish word. You meet it most often in history books and in law: a general seizes the throne, so writers call his rule a usurpation; a king's brother pushes the young prince aside, and that is usurpation of the crown. Because it is a noun, it names the whole event or the whole situation, not one moment — 'the usurpation of 1399' can mean the seizing itself, and also the years of rule that followed. The key idea is 'no right to it'. That is what separates usurpation from winning an election, inheriting a business, or being promoted. Someone else held the position legitimately, or should have held it, and this person took it anyway. Though actually, the word has spread well past thrones. Lawyers and journalists use it for one part of a government quietly taking powers that belong to another part: 'the usurpation of the legislature's authority by the executive'. Here nobody grabbed a crown — a president simply started deciding things that parliament is supposed to decide. You will also see it used more loosely, and a bit dramatically, for small things: a colleague who takes over your project might be accused of usurpation, half as a joke. One more thing worth knowing: the word carries judgement. Nobody describes their own act as a usurpation. It is what the losing side, or a later historian, calls it. The winner calls it a restoration, or a revolution, or simply 'taking my rightful place'.

篡奪、篡位（尤指奪取王位、政權）；引申為越權、侵奪職權