Realm x Kingdom: Qual a diferença

Is there any difference between "Realm" and "Kingdom"? I've been searching for an answer but I still haven't found it...

https://www.oxfordlearnersdictionaries. ... lish/realm
1. An area of activity, interest, or knowledge in the realm of literature At the end of the speech he seemed to be moving into the realms of fantasy.
2. (formal) a country ruled by a king or queen synonym kingdom the defence of the realm

https://www.oxfordlearnersdictionaries. ... sh/kingdom
1. A country ruled by a king or queen
The United Kingdom
The kingdom of God (= heaven)
2. An area controlled by a particular person or where a particular thing or idea is important
3. One of the three traditional divisions of the natural world the animal, vegetable and mineral kingdoms

Does exist any difference or is just a context difference?