Is because i said so a sentence fragment?

Yes, "because I said so" is a sentence fragment. Here's why:

* Missing Subject: It lacks a subject (the person or thing performing the action). For example, "Mom said because I said so."

* Incomplete Thought: It doesn't express a complete thought. It's missing the main verb that would explain why something is happening.

To make it a complete sentence, you need to add a subject and a verb:

* "Mom said, 'Because I said so!'"

* "That's why it's happening, because I said so."