The complexity of an expression is defined by the number of &&, || and condition ? ifTrue : ifFalse
operators it contains.
A single expression's complexity should not become too high to keep the code readable.
With the default threshold value of 3:
if ((condition1 && condition2) || (condition3 && condition4)) && condition5 ... end
if (myFirstCondition() || mySecondCondition()) && myLastCondition() ... end