Is it possible to have a thread that is not associated with any process in the system?

In operating systems, a thread is always associated with a process because a thread is a unit of execution within a process that uses its resources (memory, descriptors, etc.).

Therefore, a thread cannot exist without a process, as the process provides the context and address space for the thread.

In systems with low-level thread management, all threads belong to some process. In some specialized systems or within the kernel of an OS, there may be threads or tasks not related to user processes, but in the general understanding and in user systems, a thread is always linked to a process.