Hello Ramon, I didn't have any idea how to answer this. Hello Ramon, I hadn't any idea how to answer this. ... but I decided to try! They can have exactly the same meaning. I did not have = I had not I didn't have a cold (atishoooo!) last week ... would be more commonly said than.... I hadn't a cold last week. I didn't have to go to school yesterday... would be more commonly said than.... I hadn't to go to school yesterday. But in some expressions the 'hadn't' form is often used common. "I hadn't a clue what he was talking about!" (I had no idea/no understanding = I didn't have a clue). I hadn't/had can be followed by a past participle.... I hadn't been to school all week so the school inspector came to see my mother. It was late, and I hadn't had dinner so I went out for pizza. If I had had more time, I would've studied more. If I hadn't had a toothache, I would have gone out last night.(3rd Conditional) If you change that last example to 'didn't have' then you'll change the time reference: If I didn't have a toothache, I would go out tonight.(What you've got here is a 2nd Conditional) I hope this helps. I HADN'T realized that I DIDN'T HAVE many ideas on this topic. Or, in other words, I DIDN'T realize that I HADN'T many ideas. (Can you draw timelines for the 'thought' and the 'realization' for these two sentences? They're a bit different!). Any more ideas from other teachers and students? MW.

I didn't have you. I hadn't owned you. If in that case, they are the same in meaning. If concerning about grammar then the explanation from Jmat is right.

"I didn't have..." indicates possession. 'Have' isn't an auxiliary verb here. "I hadn't...." is used with a perfect tense. Here 'have' is an auxiliary verb.