Scale-free network
A scale-free network is a network whose degree distribution follows a power law, at least asymptotically. That is, the fraction P(k) of nodes in the network having k connections to other nodes goes for large values of k as P ( k ) ∼ k − γ {\displaystyle P(k)\ \sim \ k^{\boldsymbol {-\gamma }}} where γ {\displaystyle \gamma } is a parameter whose value is typically in the range 2 < γ < 3 {\textstyle 2<\gamma <3} (wherein the second moment (scale parameter) of k − γ {\displaystyle k^{\boldsymbol {-\gamma }}} is infinite but the first moment is finite), although occasionally it may lie outside these bounds.