Because the study of emergent systems crosses so many disciplines, it is useful to have a glossary. Add (in alphabetic order) words to which you feel others might need a reference, or list words or phrases that you would like to have a definition.

emergence/emergent

"refers to a property of a collection of simple subunits that comes about through the interactions of the subunits and is not a property of any single subunit.... Usually the emergent behavior is unanticipated and cannot be directly deduced from the lower-level behaviors." [2]

See  plato.stanford.edu/entries/properties-emergent/ for a historical and philosophical treatment.

Gaia

The philosophy that the earth and its biosphere is a living organism (and thus a self-regulating, self-constructed emergent system).

Hamiltonian dynamics

non-equilibrium thermodynamics

The description of a state that is not uniform; away from equilibrium. Statistical mechanics is not a good tool for describing these systems. (This is the term Physicists use to describe complex adaptive systems).

phase transition

A large, global change occurs quickly in a system with little or no intermediate forms. Often, the global change occurs through small, local, gradual changes. Example: water goes through a phase transition when heated to steam.

simulated annealing

Based on a metaphor with annealing, the process of heating and cooling a metal such that the molecules come to rest in a tightly coupled manner, used, for example, in making a sword strong. Simulated annealling in a computer program often follows a regimented schedule whereby a "temperature" parameter is slowly lowered, and randomness is slowly diminished. This helps systems settle in optimum areas, and helps to avoid local maxima.

statistical mechanics

"...the mechanics of large assemblies of (relatively) simple systems such as molecules in a gas, atoms in a crystal, photons in a laser beam, stars in a galaxy, cars on a highway, people in a social group, and so on. The main purpose of this science is to understand the behavior of the assembly as a whole in terms of the behavior of its constituents." [1]

stigmergy

Communicating by altering the environment. There are problems with this definition (since all comunication is performed by altering the environment). See [3] for a bibliography that emphasizes that people use the term in a number of different ways.

References

[1] Balescu, Radu. (1975) Equilibrium and nonequilibrium statistical mechanics. John Wiley & Sons.

[2] 'Computational Beauty of Nature', p. 449

[3]  Stigmergy Bibliography