* General "stream": No, "stream" is a common noun, referring to a flowing body of water.
* Specific stream: Yes, if you're referring to a named stream, then it becomes a proper noun.
For example:
* Common noun: "I love to walk by the stream."
* Proper noun: "The Mississippi River is a large stream."
Let me know if you have a specific stream in mind, and I can tell you whether it's a proper noun.