able本身作形容词。
able:adj.能;能够;有才智的;有才能的;(某方面)擅长的
You need to be able to work as part of a team.
你必须能作为团队的一员去工作。
They were able to come and go at will.
他们能够来去自由。
They were able to achieve a settlement without using military force.
他们没有诉诸武力就解决了问题。