Which type of error occurs during the execution of a program, often leading to unexpected behavior?

A runtime error occurs during the execution of a program, often leading to unexpected behavior or a crash. This type of error happens when the code is syntactically correct and compiles successfully, but an operation fails while the program is running. Examples include attempting to divide by zero, accessing an out-of-bounds index in an array, or running out of memory.

Runtime errors are particularly troublesome because they may not occur until a specific set of conditions is met, making them difficult to diagnose. Unlike syntax errors, which prevent the code from compiling, or logic errors, which may produce incorrect results without crashing, runtime errors disrupt the normal flow of execution and can lead to a complete halt of the program or unexpected outputs, severely impacting user experience and program reliability.