Here are some examples of words that contain this root:
* Mermaid: A mythical creature that is half human and half fish.
* Merman: A mythical creature that is half human and half fish, but male.
* Submerge: To go underwater.
* Immerse: To be completely surrounded by something, often a liquid.
* Meridian: An imaginary circle on the Earth's surface that passes through the North and South poles.
The root word "mer" is used in many different contexts, but it always relates back to the idea of water and the sea.