Take a look at these two examples: You come home with several heavy bags, and see that all your family are sitting watching TV. You say: 'Can someone help me?' In this situation, you KNOW that someone is capable of helping you. You are simply making a request for a person to help. However, if you have a difficult problem with the software on your computer, you would say: 'Can anyone help me?' In this situation, you DON'T KNOW whether anyone can help or not. Maybe nobody can help you. If I say 'Do you know someone in London?', I already have a pretty good idea that the answer is yes - I'm just maybe checking who it is that you know. Whereas if I say 'Do you know anyone in London?', I think that there is at least a 50% possibility that the answer will be 'no'. Remember - when you say 'anyone', you always have the possibility of 'no one' in your mind. The same goes for all the 'any' words - anywhere, anything etc. By the way, if you look at it from an English-speaker's perspective, when we are learning French we all ask at some point 'How do you say 'anybody' in French? We know that 'somebody' is 'quelqu'un', but how do you say anybody? There doesn't seem to be a French word.' And the best answer that our French teachers give is 'n'importe qui' : it doesn't matter who - just anyone. I hope that helps!