1. able, capable, competent

able為常用詞，指具有做某事所需的力量，技巧，知識與時間等，一般下效率無關，用作定語表示能力超出平均水平。如：A cat is able to see in the dark.

capable 指滿足一般要求的能力，可以是表現(xiàn)出來的，也可是潛在的，搭配是be capable of +doing。用作定語，表示的能力沒有able表示的能力強。如：He is capable of running a mile in a minute. He is a very capable doctor.

competent 指“勝任”，“合格”，或受過專業(yè)技術(shù)等訓練的，但不是超群的能力。如：A doctor should be competent to treat many diseases.

2. aboard, abroad, board, broad

aboard 在船(或飛機，車)上。如：I never went aboard a ship.

abroad 副詞，在國外或海外。如：He often goes abroad.

board 為動詞，上(船，飛機，車)。如：The passengers are boarding the plane now.

broad 為形容詞，寬廣的。如：He has very broad shoulders.