Ⅰ. can “能”表過去或現(xiàn)在“能力所及”時(shí)，與be able to 通用。如：
① He can / is able to speak German. 他會(huì)說德語。
② He could / was able to run very fast when I was a boy. 我小時(shí)候就跑得很快。
Ⅱ. be able to 的過去時(shí)還可表一種“經(jīng)過努力做到了”的意思。而can的過去時(shí)則沒有這種意義。如：
He started late, but he was able to catch the eight o’clock train. 他出發(fā)晚了，但他還是趕上了八點(diǎn)鐘的火車。
Ⅲ.can 通常只用于上述兩種時(shí)態(tài)，而be able to 則可用于各種時(shí)態(tài)。如：
He has not been able to come since he got hurt. 自從受傷以后，他就一直未能前來。
Ⅳ. 在表猜測(cè)時(shí)，只能用can，而不能用be able to ，如：
That can’t be your bag. 那不可能是你的書包。
① He can / is able to speak German. 他會(huì)說德語。
② He could / was able to run very fast when I was a boy. 我小時(shí)候就跑得很快。
Ⅱ. be able to 的過去時(shí)還可表一種“經(jīng)過努力做到了”的意思。而can的過去時(shí)則沒有這種意義。如：
He started late, but he was able to catch the eight o’clock train. 他出發(fā)晚了，但他還是趕上了八點(diǎn)鐘的火車。
Ⅲ.can 通常只用于上述兩種時(shí)態(tài)，而be able to 則可用于各種時(shí)態(tài)。如：
He has not been able to come since he got hurt. 自從受傷以后，他就一直未能前來。
Ⅳ. 在表猜測(cè)時(shí)，只能用can，而不能用be able to ，如：
That can’t be your bag. 那不可能是你的書包。