Second-Order Circuit

Q: What is a 2nd-order circuit?

A: A 2nd-order circuit is a circuit in which any voltage/current inside the circuit may be described by a 2nd-order differential equation:

$\frac{d^2x(t)}{dt^2}+c_1\frac{dx(t)}{dt}+c_0x(t)=f(t)$

where $c_1$ and $c_0$ are constants