Condition

A condition is a specification of the current states of cells in some cell's neighbourhood, under some equivalence class. For example, one can write:

- 'B3' to denote the condition "the cell is currently dead and has exactly three alive neighbours and all its other neighbours are dead"

- 'S3' to denote the condition "the cell is currently alive and has exactly three alive neighbours and all its other neighbours are dead".

- The digit '3' can denote the condition "the cell has three alive neighbours and all its other neighbours are dead".

Using Hensel notation, one can write 'S4c' to denote the condition "the cell is currently alive and it has four alive neighbours, all diagonally adjacent to the cell, and four dead neighbours, all orthogonally adjacent to the cell".

Atomic components of rulestrings such as 'B3' or 'S4c' are often referred to as transitions, because they contain slightly more information than just a simple specification of the current states of cells. The "B" or "S" prefix also specifies the future state of the key cell.

The term "transition" for this combination of information -- i.e., current condition and future cell state -- may have originated partly from the longer term "transition rule", and partly from the term "transition table", the main part of a Golly rule table definition where each line specifies a "transition" in this sense of the term.