[vishnugupta]

The way I wrap my head around this is "open" == "no defined beginning or end point" and "closed" == "precisely defined beginning/end point".

To take your thinking a bit further the interval is "shut" precisely because it's closed exactly at that point. And the interval is thrown "open" by not including the point.

BTW; Rudin's classic text (1) covers the fascinating topic of neighborhoods which builds on the concept of intervals. It took me a while to completely understand the concept but after that understanding limits was relatively easier; even otherwise "neighborhood" as a concept is interesting in itself.

[1] http://www.math.boun.edu.tr/instructors/ozturk/eskiders/guz1...

[matthewcanty]

My word, I'd have to do some studying to get through that!

Thanks for everyone's input. I think I have a clear understanding of the open/closed paradigm now.