Simultaneity is the property of two events happening at the same time

Time

Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

 in at least one frame of reference

Frame of reference

A frame of reference in physics, may refer to a coordinate system or set of axes within which to measure the position, orientation, and other properties of objects in it, or it may refer to an observational reference frame tied to the state of motion of an observer.It may also refer to both an...

. The word derives from the Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 simul, at the same time (see sem-1 in Indo-European Roots) plus the suffix -taneous, abstracted from spontaneous (which in turn comes directly from Latin).

The noun simult means a supernatural coincidence

Coincidence

A coincidence is an event notable for its occurring in conjunction with other conditions, e.g. another event. As such, a coincidence occurs when something uncanny, accidental and unexpected happens under conditions named, but not under a defined relationship...

, two or more divinely inspired

Hierophany

The term "hierophany" signifies a manifestation of the sacred.-In Mircea Eliade's writings:...

 events that occur at or near the same period of time

Pre-established harmony

Gottfried Leibniz's theory of pre-established harmony is a philosophical theory about causation under which every "substance" only affects itself, but all the substances in the world nevertheless seem to causally interact with each other because they have been programmed by God in advance to...

 that are related to each other in both noticeable and unnoticeable characteristics.

• In econometrics
  Econometrics
  Econometrics has been defined as "the application of mathematics and statistical methods to economic data" and described as the branch of economics "that aims to give empirical content to economic relations." More precisely, it is "the quantitative analysis of actual economic phenomena based on...
  
  , it arises when one or more of the explanatory variables is jointly determined with the dependent variable, typically through an equilibrium
  Economic equilibrium
  In economics, economic equilibrium is a state of the world where economic forces are balanced and in the absence of external influences the values of economic variables will not change. It is the point at which quantity demanded and quantity supplied are equal...
  
   mechanism.
• In criminal law
  Criminal law
  Criminal law, is the body of law that relates to crime. It might be defined as the body of rules that defines conduct that is not allowed because it is held to threaten, harm or endanger the safety and welfare of people, and that sets out the punishment to be imposed on people who do not obey...
  
  , for a criminal violation to be established, it usually must be shown that there was simultaneity
  Concurrence
  In Western jurisprudence, concurrence is the apparent need to prove the simultaneous occurrence of both actus reus and mens rea , to constitute a crime; except in crimes of strict liability...
  
   of actus reus
  Actus reus
  Actus reus, sometimes called the external element or the objective element of a crime, is the Latin term for the "guilty act" which, when proved beyond a reasonable doubt in combination with the mens rea, "guilty mind", produces criminal liability in the common law-based criminal law jurisdictions...
  
   and mens rea
  Mens rea
  Mens rea is Latin for "guilty mind". In criminal law, it is viewed as one of the necessary elements of a crime. The standard common law test of criminal liability is usually expressed in the Latin phrase, actus non facit reum nisi mens sit rea, which means "the act does not make a person guilty...
  
  .
• In mathematics
  Mathematics
  Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
  
  , a system of equations or a set of simultaneous equations
  Simultaneous equations
  In mathematics, simultaneous equations are a set of equations containing multiple variables. This set is often referred to as a system of equations. A solution to a system of equations is a particular specification of the values of all variables that simultaneously satisfies all of the equations...
  
   share variables; a solution is a set of variable values for which all these equations are satisfied together.
• In music
  Music
  Music is an art form whose medium is sound and silence. Its common elements are pitch , rhythm , dynamics, and the sonic qualities of timbre and texture...
  
  , see Simultaneity (music)
  Simultaneity (music)
  In music, a simultaneity is more than one complete musical texture occurring at the same time, rather than in succession. This first appeared in the music of Charles Ives, and is common in the music of Conlon Nancarrow and others....
  
  .
• In physics, see Relativity of simultaneity
  Relativity of simultaneity
  In physics, the relativity of simultaneity is the concept that simultaneity–whether two events occur at the same time–is not absolute, but depends on the observer's reference frame. According to the special theory of relativity, it is impossible to say in an absolute sense whether two events occur...
  
  .
• In marketing
  Marketing
  Marketing is the process used to determine what products or services may be of interest to customers, and the strategy to use in sales, communications and business development. It generates the strategy that underlies sales techniques, business communication, and business developments...
  
  , simultaneity is one of the characteristics of a service which differentiates it from a product. It refers to the idea that the production and consumption of a service occur simultaneously, making it impossible to produce and store a service prior to consumption.