Hello everybody, I've searched and seen hundreds of threads about both of the above terms, but I can't find one which directly compares and contrasts the two. I would say that in most cases they are interchangeable, eg: Have you been here for a long time/long?/They won't stay for a long time/long. But not always, and I'm having a hard job to explain to my students when and why. For example, I don't like the sound of long in the following sentences: It's (been) a long time time I saw him I haven't seen him for a long time It takes me a long time to get ready We waited for a long time (but have you been waiting long? sounds fine to me) I can't work out any theory about verb tenses, types of verbs etc. that it is consistent with all the examples. Any comments would be appreciated.