Here's how it works in your examples:
* Kingdom: "King" is the root word, and "-dom" adds the idea of the "state of being ruled by a king."
* Freedom: "Free" is the root word, and "-dom" adds the idea of the "condition of being free."
Here are some other words with the "-dom" suffix:
* Wisdom: The state of being wise
* Freedom: The state of being free
* Christendom: The state of being Christian
* Wilderness: The state of being wild
* Kingdom: The state of being ruled by a king
Let me know if you'd like to explore other suffixes!