Operations

Examples: additions, multiplications, comparisons

Constant time C_i per i^th line of pseudocode

In reality each operations takes different amount of time

Best Case: constraints on the input, other than size, resulting in the fastest possible running time

Worst Case: constraints on the input, other than size, resulting in the slowest possible running time

Average Case: average running time over every possible type of input (usually involves probabilities of different types of input)