\begin{definition}[Definition:Fork]
Let $T$ be a complete $\LL$-theory.
Let $\mathfrak C$ be a monster model for $T$.
Let $A$ be a subset of the universe of $\mathfrak C$.
Let $\map \pi {\bar x, \bar b}$ be a set of $\LL$-formulas with free variables $\bar x$ and parameters $\bar b$ from the universe of $\mathfrak C$.
{{Disambiguate|Definition:Logical Formula}}
$\map \pi {\bar x, \bar b}$ '''forks''' over $A$ {{iff}} it implies some disjunction $\map {\phi_1} {\bar x, \bar c_1} \vee \cdots \vee \map {\phi_n} {\bar x, \bar c_n}$ where each $\map {\phi_i} {\bar x, \bar c_i}$ divides over $A$.
An individual formula $\map \phi {\bar x, \bar b}$ is said to '''fork''' {{iff}} the singleton $\set {\map \phi {\bar x, \bar b} }$ forks.
\end{definition}