The notation "h(a)" typically represents a function named "h" evaluated at a specific input "a." In mathematics, functions are rules that assign each input a unique output. For example, if h is a function that doubles its input, then h(3) would equal 6. In various contexts, "h(a)" can also refer to specific applications, such as in computer science, where it might denote a hash function. A hash function takes an input (like "a") and produces a fixed-size string of characters, which is often used in data structures like hash tables for efficient data retrieval.