The Most Honourable Order of the Bath (formerly The Most Honourable Military Order of the Bath) is a British order of chivalry founded by George I on 18 May 1725. The name derives from the elaborate mediæval ceremony for creating a knight, which involved bathing (as a symbol of purification) as one of its elements. The knights so created were known as Knights of the Bath. George I "erected the Knights of the Bath into a regular Military Order". He did not (as is often stated) revive the Order of the Bath, since it had never previously existed as an Order, in the sense of a body of knights who were governed by a set of statutes and whose numbers were replenished when vacancies occurred.

The Order consists of the Sovereign (currently Elizabeth II), the Great Master (currently H.R.H. The Prince of Wales), and three Classes of members:

Members belong to either the Civil or the Military Division. Prior to 1815, the order had only a single class, Knight Companion (KB), which no longer exists. Recipients of the Order are now usually senior military officers or senior civil servants. Commonwealth citizens not subjects of the Queen and foreigners may be made Honorary Members.

In mathematics, big O notation is used to describe the limiting behavior of a function when the argument tends towards a particular value or infinity, usually in terms of simpler functions. It is a member of a larger family of notations that is called Landau notation, Bachmann–Landau notation (after Edmund Landau and Paul Bachmann), or asymptotic notation. In computer science, big O notation is used to classify algorithms by how they respond (e.g., in their processing time or working space requirements) to changes in input size.

Big O notation characterizes functions according to their growth rates: different functions with the same growth rate may be represented using the same O notation. A description of a function in terms of big O notation usually only provides an upper bound on the growth rate of the function. Associated with big O notation are several related notations, using the symbols o, Ω, ω, and Θ, to describe other kinds of bounds on asymptotic growth rates.

Big O notation is also used in many other fields to provide similar estimates.