Asymptotic Analysis
Asymptotic analysis is depending on the idea that as the problem size grows, the complexity can be defined as a simple proportionality to some known function. This idea is incorporated in the "Omega", "Big O" and "Theta" notation for asymptotic performance.
The notations such as "Little Oh" are similar in spirit to "Big Oh" ; but are hardly ever used in computer science for asymptotic analysis.