We usually use "otherness," like this: "Since the very beginning of time, humans have always formed groups that define themselves according to certain attributes and exclude people due to their "otherness." So, yes, it is similar in meaning to differences - you could replace "otherness," in the sentence above with differences and the sentence would still have the same meaning. Discrepancy has a different meaning. A discrepancy is something that isn't quite right - for example if a restaurant's order tickets show that it should have made £1,000 during the night, but the amount of money in the till and/or taken by cards is only £950, then we would say that there "is a discrepancy here."