"You have my word" is basically the same as "I promise". However if you tell someone "You have my word on that.", you have made a statement that is more dramatic and carries more weight, emotionally. If I tell someone that somebody has broken a promise, his first reaction might be to ask what the promise was. The final judgment might depend on what was promised. However, if I say that somebody has broken their word, the first reaction would be to pass judgement on the that person's honor. The first reaction would be much stronger and more final. While this is not true in all cases, there would definitely be a tendency to put more weight on someone's word than their promise.

sorry,answer was for other! but my PC keeps freezing on some one else!(some times) Sincerely

Yes, it does.

it is adverb in spoken informal 1. used to say that you have exactly the same opinion as someone else: ‘I hated school.’ ‘Ditto.’ ------------------------------------------------------------------------------------------------------- 2. used to say that what is true of one thing is also true of another: Where should she go? Mississippi? Too hot. Ditto Alabama. ===================================================== **)ditto mark is noun (plural dittoes) [countable] in written it is an Italian word; a mark (〃) that you write immediately under a word in a list to show that the same word is repeated