Negative prefixes are very productive. It seems that if you learn these then you might be able to create countless English words. However, it is not enough to learn only the prefixes.
Present simple tensecor Present simple or present continuous tense improved
As I mentioned before, next year I am going to teach low level students, so I am trying to prepare some materials which I will be able to use with them. A week ago I wrote a post on the verb to be in .