Inquiry Based Science Talk

I may be showing my age here, but when I was a student in high school, no one thought to ask the question, "What is a textbook?".  The definition was fairly straightforward, and all textbooks looked pretty much the same.

Times have changed.  I recently attended a webinar hosted by the Texas Education Agency outlining processes and procedures for textbook adoption to school textbook publishers.  We were reminded throughout the presentation that the definition of a textbook had been broadened to reach far beyond the traditional printed book.  The term textbook, whether it refers to textbooks for elementary school or secondary school textbooks, can include nearly anything that "conveys information to the student or otherwise contributes to the learning process" (retrieved from http://ritter.tea.state.tx.us/textbooks).

This leaves the door open for all types of digital media and certainly some formats we haven't even though of yet!  How does your school or district define the textbook?