Ability (/əˈbɪləti/) is the capacity of having the means or skill to do something.
In English, ability is often expressed using the full modal verb "can", and its preterite "could". It's also possible to use the lexical-grammatical structure "be able to", particular as an infinitive (i.e. "to be able to") or as a gerund "being able to", since being a full modal verb "can" lacks an infinitive and gerund.
For someone (e.g. a child) who is subordinate to another person (e.g. an adult), ability is often strongly associated with permission. e.g. Hence a child will ask "can I watch a cartoon?" when they mean "Will you give me permission to watch a cartoon that I would like to watch?"