Explain the difference between a process and a thread. In your explanation, discuss their states, lifecycle, and how they interact in a multithreaded application. Furthermore, examine the implications of using threads in memory management.

A process is an independent program executing in its own memory space, while a thread is the smallest unit of execution within a process, sharing the same memory space with other threads of the same process. Threads are lightweight compared to processes, which lead to less overhead. In terms of lifecycle, a process can be in various states like new, ready, running, waiting, and terminated, while a thread can be in states like new, runnable, blocked, and terminated. In a multithreaded application, threads can communicate with each other through shared memory, allowing for efficient data exchange, but this requires careful regulation to prevent issues like data races and deadlocks, showing the importance of synchronization mechanisms.