Big Omega notation (Ω) is used to represent tight lower bound.If a function f(n) is equal to Ω(g(n)), it means f(n) is always greater than C(g(n)).Big Theta notation (Ø) represents the average case for a function.If a function f(n) is equal to Ø(g(n)), it means f(n) is greater than C1(g(n)) and less than C2(g(n)) for all n>= 0.