1. Mutual Exclusion: Only one thread should be allowed to execute within the critical section at a time.

2. Progress: If no thread is executing in the critical section, and multiple threads want access, the selection of the next thread to enter should be fair.

3. Bounded Waiting: A limit should be placed on the number of times other threads can enter the critical section after a thread has requested access.

1. Locks

2. Semaphores

3. Monitors: High-level synchronization constructs that encapsulate shared data and control access through condition variables.

Deadlock: A situation where two or more threads are stuck waiting for each other to release resources, causing the system to halt.

Starvation: A situation where a thread continuously gets deprived of accessing a critical section due to other threads' priority.

Database management systems, operating systems, concurrent data structures, parallel processing, etc.