Hello, To extend the excellent point above about slim having a better connotation than thin in regards to people. I would also add that, both the words may be used in other contexts in different ways too. So thin is used as a description of an unhealthy level of bodyweight. In probability we would say, there is a slim chance of winning (not a thin chance of winning). Talking about objects, we would not normally say it is slim, normally we would say it is thin, like a thin paintbrush or a thin piece of paper. There are always exceptions, but normally this is the case. Thin is also used in other contexts, like weather, we would say, at the top of a mountain, the atmosphere is thin. So in addition to the human the uses for humans, one implying that someone is of a healthy weight (slim), and the other implying someone is underweight (thin), there are also a range of other contexts in which these words differ. I hope this helps, Best regards, Shaun.

The words mean the same thing, but "slim" has a positive connotation, and the word makes often suggests attractiveness. "thin" doesn't connote attractiveness, and can easily be used in a negative context: "He's thin as the result of his cancer."

thin is probably thinner than slim. Maybe you could say when slim people lose weight they get thin.

They are both the same.