> My writing teacher told me that a proper haiku is about the seasons; the same form on any other subject is a senryu.

From the Columbia Electronic Encyclopedia, via Atomica:

Senryu: a Japanese poem structurally similar to the haiku but primarily concerned with human nature. It is usually humorous or satiric. Used loosely, the term means a poem similar to the haiku that does not meet the criteria for haiku.

Haiku: an unrhymed Japanese poem recording the essence of a moment keenly perceived, in which nature is linked to human nature. It usually consists of 17 jion (Japanese symbol-sounds). The term is also used for foreign adaptations of the haiku. These poems are usually written in three lines of five, seven, and five syllables.

-Faux "finder of things" Pas