Open sets truly
Are in the topology;
How very useful.

Comments: I wrote this haiku, understandably enough, during my Topology class. It refers to the fact that open sets can be defined many different ways, and they are defined (in Topology) simply to be members of a set (called the topology). When first confronted with some theorems concerning open sets, my initial reaction was not enthusiastic. I started my proof assuming that a set was open, and then tried to progress from there. Inevitably I would cry out “Christ on a horse!” to indicate my frustration to all the gods of heaven and earth. Eventually I came to appreciate the simplicity of the definition (and how it could actually be used in a proof), but I still wrote this haiku to commemorate my struggle.