title_body: Does a session beer have to be below a specific ABV?
upvoted_answer: Like many beer terms, "session beer" is not rigorously defined.  Several groups have tried, though:
  
  
  The Brewers Association (PDF) called it 4.0-5.1% ABV
  Beer Advocate calls it less than 5%
  The Session Beer Project calls it 4.5%.
  
  
  Really, though, if you call something a session beer, most people will understand that to mean something you could easily drink several of in a session (ie, lighter and more mild than a "big" beer).