What type of punctuation is not used internally in a senctence?

The punctuation mark that is not used internally in a sentence is the period (.).

Here's why:

* Periods are used to mark the end of a sentence. They signal that the thought is complete.

* Other punctuation marks like commas, semicolons, colons, and question marks are used within a sentence to organize its structure and meaning.

Let me know if you'd like to explore other punctuation rules!