What is he root word for curious?

The root word for "curious" is "cura", which is Latin for "care" or "concern".

Here's how it works:

* "Cura" evolved into the Latin word "curiosus" meaning "inquisitive" or "careful".

* "Curiosus" then became the English word "curious".

So, "curious" literally means "full of care" or "concerned about" something, which is why it's often associated with wanting to learn more or investigate.