If you’re a beer drinker (and even if you’re not), chances are you’ve seen the word “session” on a can, bottle, or tap list, often preceding the beer world’s three favorite letters: IPA. Definitions of “session beer” abound on the internet, from stories of sustaining World War I shell factory workers, to low-proof beers that pair well with weed.

The most common use of “session” in beer contexts is as a qualifier. It means the beer in question contains low enough amounts of alcohol that several, or even many, can be consumed in one drinking “session.” The term “sessionable” is commonly used to suggest something is easily drinkable, light, refreshing, or any combination of the three.

But even those airy definitions leave a lot open to interpretation. As all beer drinkers are different, with individual sizes, appetites, tolerances, and preferences, how can we say what “session” or “sessionable” even means?

In a post on his blog Zythophile, British beer writer and historian Martyn Cornell suggests the concept of a session beer has only been around since the 1980s. According to his research, the first recorded uses were from 1991: “One in Britain, where someone in the magazine of the Institute of Practitioners in Work Study, Organisation, and Methods wrote: ‘A good tip is to pour it into a jug first, leaving the sediment in the bottle, thus enabling you to share the contents with your colleagues, which I would certainly commend, as this is definitely not a session beer,’” Cornell writes.

Another came from the U.S. “Steve Johnson, in ‘On Tap: The Guide to U.S. Brewpubs,’ wrote: ‘Session beer: Any beer of moderate to low alcoholic strength,’” Cornell adds

According to the Beer Judge Certification Program (BJCP) Style Guidelines, the suggested strength of a session beer is less than 4 percent alcohol by volume (ABV). According to U.S.-born, London-based podcaster, beer sommelier, and author Natalya Watson, this isn’t a rigorous, strict definition.

“In my understanding, there is no formal definition for a session-strength beer and, in reality, I’d say most American consumers consider beers below 5 percent ABV to be of session strength. While most British consumers are more likely to agree with the BJCP guideline of less than 4 percent,” Watson says.

Beer writer and judge Melissa Cole agrees. “I’ve come to the conclusion that it’s a very parochial thing. When I learned to love beer in the north of England, nothing above 3.8 percent would have even entered into the idea of a session beer,” she says. “If I had to nail my colors to the mast on a definition, I’ll always go back to the sub-4-percent idea.”

John Harris, the founder of Ecliptic Brewing in Oregon, believes session beers sit “generally below 5 percent for normal beer.” When I asked what the word means to him, he replied, “in the beer world, it means high drinkability.”

Regardless of which side of the Atlantic you sit on, it appears that “session” still refers to a low strength. Unless, of course, you happen upon a Session Imperial IPA, Imperial Session IPA, or Session Barleywine, such as Space Ghost, a Golden Session Barleywine Ecliptic collaboration beer that, by Harris’s own admission, isn’t a Barleywine at all. At 8 percent ABV, it’s not what would commonly be considered sessionable, either.

But to be sessionable, does a beer simply have to be of a low strength? James Rylance, head of the U.K.’s Harbour Brewing’s experimental program, who was instrumental in creating the now-ubiquitous Neck Oil, Beavertown Brewery’s first Session IPA, doesn’t agree.

“The easy answer with sessionability is about ABV, but I think that’s not really understanding it enough,” he says. “Sessionability is about balance. You probably don’t really have many sessionable beers that are 8 percent, but you also you don’t have many balanced beers that are 8 percent. I think, in the U.K., we have the concept of sessionability must mean a whole day drinking pints, and it must be a certain thing. In other parts of the world, there’s less of that ‘single unit of measurement; must come in a pint.’

“I think ‘sessionable’ is a beer that can be drunk repeatedly, multiple times, in its correct volume. There’s a lot of Belgian beers that are super sessionable, like Saison Dupont at 6-point-something percent — that’s sessionable, but I’m just not drinking a pint of it. And that’s a beautifully balanced beer,” Rylance adds.

Does that mean that sessionable beer is more than just low-strength and refreshing? For example, is a lighter, weaker, mass-produced lager less sessionable than a Session IPA? It depends on what you’re looking for, Rylance says. “I think that’s true of people who are looking for flavor,” he says, but others probably think “the perfect definition of sessionable, statistically, is probably something like Carling. It’s probably the session beer.”

Indeed, the very concept of a session IPA only exists within the context of craft beer: If you were to walk into a bar pouring only Budweiser, Carlsberg, and Coors Lite and ask for a sessionable beer, you’d likely be met with blank stares.

“The words ‘Session IPA’ only exist because a lot of things aren’t sessionable. But when you live in a world where everything is Carling and Strongbow and Guinness, everything’s sessionable,” Rylance says. “Why the f*ck would you have a 7 percent beer?”

As craft beer continues its often-confusing growth, will we see a rise in session double IPAs? “That’s bullsh*t,” Rylance laughs. “Yeah, that is bullsh*t. But it’s an interesting thought, though, isn’t it?”

Even the very concept of a session is changing, albeit slowly. As modern beer cultures grow, attitudes toward drinking are evolving, and so, too, is the idea of a session developing.

“A ‘session’ is no longer about everyone ordering the same 4 to 5 percent lager rounds for everyone in the group,” says Chris Hannaway, founder and CEO of alcohol-free brewery Infinite Session. “There’s a world of choice now, and people can drink 0 to 14 percent-plus beers interchangeably, and go at whatever pace they fancy on that round, night, week, or whenever.”