"Ω(n log n)" is a notation used in computer science to describe the lower bound of an algorithm's running time. It indicates that, in the best-case scenario, the algorithm will take at least a time proportional to n log n, where n is the size of the input. This is common in efficient sorting algorithms like merge sort and heap sort, which perform well even with large datasets. In this context, "n" represents the number of elements being processed, while "log n" refers to the logarithm of n, which grows much slower than n itself. The combination of these two factors suggests that as the input size increases, the time taken by the algorithm increases at a manageable rate, making it suitable for large-scale problems.