A correspondence whereby a superstring theory describing gravity on a certain type of space (known as Anti-deSitter space) can be mapped to a conventional supersymmetric quantum field theory without gravity on the boundary of that space. This can be exploited to simplify complex calculations in one theory by mapping them to their corresponding calculation in the other theory.

The idea that certain physical quantities have the values that they do because, had they taken different values, life would not have been possible and thus we would not be around to observe their values. This principle has been employed as one possible explanation of the string theory landscape.

Any particle with an angular momentum which takes integer values. These particles have the important property that two or more of them can occupy the same quantum state. For example, photons in a beam of light can all have the same momentum, as in a laser.

The process by which extra dimensions of space time are rendered unobservable by being "rolled up" into closed shapes with a very small radius. For example, from far away the surface of a wire appears to occupy only one spatial dimension. However upon close inspection it is revealed that the surface is actually two-dimensional, with the second dimension compactified into a very small circle.

An n-dimensional plane in string theory to which the ends of open strings are attached.

A transformation that maps the equations of one type of theory into those of another type of theory. The AdS/CFT correspondence is an example of such a duality.

A solution to the equations of string theory which describes empty space, but does not correspond to what experiment tells us empty space should look like in our universe. String theory predicts a large number of these solutions, and currently no good selection mechanism exists to find the solution that matches our universe.

Any particle with an angular momentum which takes half-integer values. These particles have the important property that no two of them may simultaneously occupy the same quantum state, a property known as the Pauli Exclusion Principle.

The idea that, although the universe in string theory is 10 dimensional, all the information contained in the universe is described by what happens at its boundaries. Originally formulated to explain what happens to information falling into a black hole, it has found some validation in the AdS/CFT correspondence.

A proposed 11 dimensional theory which reduces to the various known types of string theory in different limits. It was originally proposed to explain why so many dualities existed between various string theories. Currently, no complete formulation of M-theory is known

A universe in which, at very small scales, the actual coordinates of spacetime were quantum objects. In such a space, something like the Heisenberg uncertainty principle would hold between various direction measurements in spacetime.

An immensly successful class of theories in which particles of various types are described not as isolated points, but as localized fluctuations in a sort of field. Thus, as the photon is an excitation in the electromagnetic field, the electron becomes an excitation in the "electron field". Theories of this type have been used to great success to understand fundamental physics in the abscence of gravity. Gravity, however, is very resistant to a quantum-field-theoretic explanation, hence the search for a unifying theory such as string theory.

In its original formulations (bosonic string theory), it was a theory that described various bosonic particles as being formed by vibrations of small strings living in a 26 dimensional spacetime. More recently, however, it is a term used interchangeably with "superstring theory".

Set of all possible empty space - or vacuum - solutions to string theory, including all the false and true vacua.

One of the four fundamental fources of nature, the strong interaction is the force which binds protons and neutrons together. More generally, it is felt by all particles composed of quarks.

Any of a group of theories which attempts to generalize bosonic string theory by including supersymmetry. This allows the theory to describe both fermionic and bosonic particles, and it is hoped by some that such theroies correctly unify quantum field theory and gravity into a theory of everything.

The property of a theory whereby the fundamental equations do not change if all bosons are replaced by fermions, and all fermions replaced by bosons. Since in most standard theories there are no fermions corresponding to a specific boson and vice-versa, supersymmetric theories generally contain a large number of experimentally unobserved particles known as "super-partners" of the more well-known particles.