Threads are very similar to processes in many respects; after all, they were initially called "lightweight processes". However, there are also quite a few differences between threads and processes.

Focus on ONE such difference and list it clearly in the beginning of your post. Please explain this difference using your own words in such a way that everyone with some understanding of computers and computer programming will understand it. Include concrete examples of how that difference was implemented in certain operating systems, or how it manifests in a certain programming language are highly encouraged.

Examples could include code fragments or full examples in a certain programming language, that further clarify the discussed concepts.