Elementary reaction steps with order 3 (called ternary reactions) are rare and unlikely to occur. However, overall reactions composed of several elementary steps can, of course, be of any (including non-integer) order.
Here  stands for concentration in molarity (mol · L),  for time, and  for the reaction rate constant. The half-life of a first-order reaction is often expressed as t = 0.693/k (as ln(2)≈0.693).