Space complexity
Space Complexity is a concept in theoretical computer science, specifically Complexity Theory, which is used to measure and describe the efficiency of an algorithm in terms of the amount of memory they will require to store the information they need. Algorithms, when implemented in computer programs, require two main resources when the program is executed: time and memory. Memory, particularly, may be expensive in large quantities. Therefore it is often desirable to make modifications to an algorithm so as to reduce its space complexity, that is, make it use less memory when run.