Hello people please help me to figure out about: I have met in the past three form 'could', ' was able' and 'could have', so i know that the difference between 'could' and 'could have' is, but i don't know when i should use the 'was able' in the past. Help
Sorry but we can't help. There are many instances where could and was able are synonymous, and there isn't any general guidance on when one might be preferable to the other. You would need to provide an example sentence. Remember that in English there are almost always several ways of saying the same thing - you're not obliged to use all of them.
I know this thread is old but I'm interested in the same question. I hope that someone can help in the clarification of this. So, according to the site englishpage.com:
"Could" cannot be used in positive sentences in which you describe a momentary or one-time ability.
The example they give is "Yesterday, I could lift the couch by myself". [Not Correct]
Also they say : "Could" can be used in negative sentences in which you describe a momentary or one-time ability.
The example they give is: "Yesterday, I couldn't lift the couch by myself". [Correct]
My guess is that it is in these cases where we need to use "be able to". Is this so?