One of the questions that tends to be answered badly is "what is the difference between...", but fair is fair: it's usually asked badly. This type of question is asked of students when the teacher wants to test if they know that the things being compared are. So it is usually acceptable to just describe the two items and leave it at that. In other words, students are not usually expected to describe the actual point(s) of difference. Usually, though, the description will implicitly amount to this. In sciences students seem to have enough trouble trying to second-guess which of the many differences I think this is something that comes up in setting and marking Economics essays: that's where I first encountered it. I probably need an example: Q1. What is the difference between Pinot Noir and Pinot Meunier? A. The meunier is characterized by a white dust under it's leaves and smaller berries, while the noir has small leaves, small bunches of largish berries, and is one of the most commonly grown in the World. This is a fairly typical answer. Have I answered the question: what is the difference? Or have I just described the things? Q2. What is the difference between 6 and 7? A. one is curved while the other has all straight lines. Surely the difference is 1? Though, perhaps the subject is calligraphy - but then perhaps the difference is the rendering style: they need different strokes? Q3. What is the difference between red and blue? A. About 200nm Does this work? What the examiner is looking for will depend on the context of the question. Usually they will look for signs of understanding the subject. For Q1 I'd look for some mention that these are different varieties of grape/vine used to make wine - then go into detail about what is different about them. For Q3, perhaps establishing the context ... the answer suggests something to do with electromagnetic spectrum so say so! (Note: it could be about the chemical composition of paint or the psychological effect of wall-color on test subects.) The student finesses their (correct) answer by showing they understand what is being asked of them. It could be argued that all this is implied in the manner of the reply - but, in an assignment or an exam, is the student well-advised to rely on the marker getting this? Just a thought.