Use stream of consciousness to answer the following. Slow-wave sleep (SWS), often referred to as deep sleep, consists of stage three (combined stages 3 and 4) of non-rapid eye movement sleep. Initially, SWS consisted of both Stage 3, which has 20-50 percent delta wave activity, and Stage 4, which has more than 50 percent delta wave activity. However, as of 2008, the American Academy of Sleep Medicine (AASM) has discontinued the use of Stage four as a separate stage. Thus, the two stages are now combined as "Stage three" or N3. An epoch (30 seconds of sleep) which consists of 20 % or more slow-wave (delta) sleep is now considered to be stage three.

Which stage of sleep is represented by delta waves?
The relevant information to answer the above question is: An epoch (30 seconds of sleep) which consists of 20 % or more slow-wave (delta) sleep is now considered to be stage three. Final answer: three.