determine 和 define 的差別在哪裡？如果不好說明，請提供一些例句。

I think you may be confused because the two words seem similar in some cases.
E.g. ‘to determine boundaries’ & ‘to define boundaries’.

To determine here means to find out, to ascertain, to sort of make clear. Maybe you don’t know what the boundaries are, so you have to find out.

To define here means to set, to establish. Maybe you know what the boundaries are but other people don’t so you have to set it so that they will know. Or maybe you don’t really know what the boundaries are yourself so you try to set the boundaries to better know what they are.

Generally, ‘Define’ is about explaining and outlining something. ‘Determine’ is about choosing and finding out things.

Hope this helps!