Don't ask for a lemon in India

Apparently, according to my friend Rathin, Indian's call both lemons and limes, "Limes". They have different species of limes - unfortunately my Hindi doesn't stretch far enough to be able to name them. But, as far as they are concerned, lemons are just a variety of limes. I found this quite fascinating. I had always assumed that they were somehow different types of fruit. Suddenly I find myself question all sorts of categorisations which I must be carrying around. Are cats and dogs really different types of animals or did I just pick up a categorisation scheme, early on in life, which then shaped my thinking. What are categories are you using, and what would the world look like if you suddenly changed them?