# What is a hazard rate?

What is the definition of a hazard rate? What is a hazard function?

I thought it was the probability that a unit does not survive the time period conditional on being alive, but I see hazard rates above one when I compute hazard rates myself and in examples of survival analysis (e.g. p.10 of http://courses.washington.edu/b515/l16.pdf). How can the hazard rate be above one if it is a probability?