Here's how:
Verb: The base form of the verb is "frighten". "Frightening" is the present participle form, used to describe an ongoing action:
* *The loud noises are frightening the children.*
Adjective: "Frightening" describes something that causes fear:
* *The movie was so frightening, I had to cover my eyes.*
Not a noun: There's no noun form of "frightening". If you want to use it as a noun, you would need to say "the frightening" (using it as an adjective before a noun).
Let me know if you have any more questions!