How to underline a header in jupyter notebooks

Question

I am trying to underline the following header in jupyter notebooks:

Definitions

I don't want the underline to span the entire screen.

I want the final result to be something like this

Definitions (h2)

---

The Internet: Global Network of interconnected computers that communicate via TCP/IP

How can I do this?

I have tried the following:

HTML underline: ## Definitions

3+ underscores

Definitions

---

3+ dashes

Definitions

---

All of these result in the horizontal line spanning the entire screen

Answer 1

Based on this answer to 'Get underlined text with Markdown' here:

## <ins>Definitions</ins>


The Internet: Global Network of interconnected computers that communicate via TCP/IP

Results in: