If speaking or writing to someone and it becomes apparent they did not interpret something correctly, is it correct to inform them "you misunderstood" or "you misunderstand"? I'm not sure because the faulty assumption took place in the past but the person is still under the influence of the faulty assumption. On a related note, I was taught that when speaking of something that could happen it is spoken in the past tense but then why does it sound so unnatural to say something like "Since Bob is not a native English speaker he will surely misunderstood the meaning of the letter"?
Learn English – “misunderstand” vs “misunderstood”
past-tenseword-usage
Best Answer
I would choose You misunderstood because, as you say, this is an action that happened in the past: it happened when that person interpreted whatever. Besides, it sounds more polite to say You misunderstood (you made one mistake) than You misunderstand (you continue making the same mistake).
As for your second question, it does not sound unnatural: it is plain wrong. I don't know exactly what you were taught, but you cannot construct the future tense using the past tense. Of course, if it is something that could have happened, you would just write: