Hi Reza, My take on this is that it is most likely a smell from a perfume or fragrance. There are some particular mixtures or elements of perfumes that can smell like this to some people. It could only be some people (small percentage) who register the particular smell and there could be many other people around who do not get this note of smell from it, including the wearer. Sometimes weather/ humidity and temperature can change how this stuff smells and then factors like skin and sweat can too. As you mention it is a strong smell, I suspect this is the case - she is probably wearing something and it has wafted your way at some point. You mention friend or classmate - it is possible, if you have noticed this with more than one girl / different girls, that it could be a popular product that is fairly common and due to target market and availability, more than one girl you know is wearing it. Or if these girls are friends and in the same classes, etc, it is also likely that one introduced friends to the same product if they liked it or her friends noticed and asked. There are a couple of ways to confirm / work out if it is this: Depending on situation / interactions and it could be tricky to navigate. - You can ask her what she is wearing / if she is wearing something. Now I would also note here, that if you ask for "what" it is, there are plenty of fragrances with names which can be in other languages, have ambiguous names or completely fictional ones or abbreviated names. You may also just get a brand name. ie. an answer like: "It is Etienne Aigner". Then the possible "nothing" answer, could also be particularly awkward, so weigh that into the risk and consider if you have a backup plan or save you can prepare. - You may prefer to go indirect and see if you can work it out. Most fragrances will have distinctive bottles that can be identifiable given a bit of looking. If you have some form of connection with her on social media, etc. then have a look for photos or videos which may have dressing tables and the like in backgrounds, see if you can spot any. Then see if you can match it up. You may be able to then find that product in a department store where you can sample it and confirm this is the smell.