Capable and able are two words that are often used interchangeably, but they actually have some differences. The word "capable" comes from the Latin word "capax," which means "able to hold" or "having the capacity." It implies that someone or something has the potential or ability to do something. For example, a person might be described as "capable of solving complex problems" or a machine might be called "capable of performing a variety of tasks."
The word "able" also means having the ability or power to do something, but it often implies a more general or inherent capacity. For example, we might say that a person is "able to run a mile" or that a bird is "able to fly."
Capable和competent也有一些区别。Competent通常指某人具备完成某项任务或工作所需的技能、知识和能力，强调的是胜任能力。一个医生可能被描述为“competent in performing surgery”，意思是他具备进行手术的能力。而capable则更强调某人有能力做某事，但不一定是在特定的领域或任务中。一个人可能被描述为“capable of learning new languages”，意思是他有学习新语言的能力。
capable和able都表示有能力做某事，但capable更强调潜力和可能性，而able更强调实际的能力和技能。在使用时，可以根据具体语境和表达需要来选择合适的词汇。
