Explanation:

For the past few days, I have learned that modal nouns are nouns that express modality. They are used to express the speaker's attitude or degree of certainty about an action or event. The words possibility, certainty, doubt, necessity, ability, and permission are some examples of modal nouns. They may mean similar to modal verbs because both express modality in a sentence. However, they are different from modal verbs because modal verbs act as the main verb in a sentence, while modal nouns modify another noun or noun phrase to express modality. For example, "John has the ability to play the guitar" uses the modal noun "ability" to modify the noun phrase "to play the guitar" to express John's capability.