Here's why:
* "Able" is an adjective: It describes a noun (e.g., "He is able to swim").
* Adverbs modify verbs, adjectives, or other adverbs: They tell us how, when, where, or to what extent something happens (e.g., "He swims quickly", "He is very able").
To create an adverb related to "able," you need to use a different word:
* "Ably" is the adverb form of "able." It means "in a competent or skillful way." Example: "He performed the task ably."
* "Capably" is another adverb that can be used in similar contexts. Example: "She handled the situation capably."
If you want to express the ability to do something, you can use the adjective "able" with a prepositional phrase:
* Example: "He is able to swim."
* This structure functions similarly to an adverb, but it's technically a prepositional phrase modifying the adjective "able."