On its surface, the beer world is fairly simple. Water, hops, malt, and yeast give you beer, and tweaking the ratios or varieties of those ingredients gives you different styles.
Listen in on a conversation between two experts, though, and you might think they're speaking a different language. Describing complex flavor profiles and brewing technicalities comes with its own unique set of lingo, and while it's far from necessary to know it all, having a working knowledge of some key terms will give you a leg up on identifying, describing, and appreciating any given brew.
To get you on your way, here are a few that you're likely to encounter in any detail-oriented beer writing or conversation. It's not an exhaustive list – brewing is full of complicated chemistry and centuries of international tradition, so covering every minute aspect is no easy feat. But it will give you a well-rounded beer vocabulary, which you can add onto as you learn.
Acetic
A tart, green apple kind of flavor. It comes from acetic acid, which sours the beer and dramatically changes the taste. It's intentional in some styles, like a Flanders Red Ale, but is otherwise considered an "off flavor" that usually comes from not properly sanitizing brewing or serving equipment.
Adjunct
Any kind of fermentable ingredient (usually corn or rice) that's used to supplement or replace malted barley in the brewing process, either to save on costs or lighten the beer's flavor. It's not inherently bad, but this is effectively a dirty word in the beer community, because it's how all those big-name light lagers are brewed, and it's part of the reason why they taste so bland.
Astringent
A harshly dry note. It's usually caused by errors in the mashing process, which results in a higher-than-usual tannin presence. The resulting flavor seems to dry out your mouth and lend a slight bitterness (just like in a very tannic bottle of red wine).
Body
The fullness of flavor and "thickness" of a beer. Thin-bodied would be like water, while full-bodied would be more like syrup.
Bottle-Conditioned
At the very end of the brewing process, most brewers carbonate their beer in great big tanks befor moving that ready-to-drink beer into bottles. An alternative method is to put the beer straight into bottles along with a little bit of sugar, which gives the beer's yeast a little extra fuel. The beer then undergoes a little bit of extra fermentation, with the yeast eating the sugars and producing carbonation. Supposedly, this also helps to further develop a beer's flavor profile.
Brett
Short for "Brettanomyces," which is a kind of "wild" yeast. That means that unlike standard brewer's yeast, which has been fine-tuned for centuries, brett can be unpredictable and produces uniquely musty and tart flavors that aren't ideal for most beers. Unsurprisingly, it's largely avoided by brewers, but can be great if you're open to the uniqely funky flavors that the stuff produces.
It's got a few different sub-types that all produce slightly different flavors, but the most common notes are a leathery funk or a sharp sourness.
Cask
Most simply, this is a precursor to the modern-day beer keg. They have a long history in England, where they're traditionally filled with unfiltered, unpasteurized beer that's conditioned in the cask (similar to "bottle-conditioned," above). It's then served with an old-style hand pump, without any additional CO2 like a standard tap uses. The resulting beer is usually cloudier, flatter, and warmer than a standard pour, which doesn't sound ideal, but casks have a devout following from tradition-minded beer drinkers.
Cicerone
Like a sommelier, but for beer. A certification program offers three levels of this distintion: "certified beer server," which is fairly easy to attain, "certified cicerone," which requires a fair bit of studying, and "master cicerone," which necessitates an extroardinary knowledge of the good stuff.
The exams test all kinds of beer knowledg, like styles, proper storage and serving, history, brewing techniques, flavor chemistry, and more. Critics say that it's more of a moneymaking venture by the certification organization than anything else, but the titles are a widely accepted benchmark of beer knowledge.
Diacetyl
A chemical that produces a buttery flavor. While it can be fine in very small doses in certain styles, the buttery note is an undesirable "off flavor" that can occur in beer where something went wrong in the brewing process.
Dry-Hopped
The standard way to add hops to beer is to boil them in the "wort" (sugary water that's a few steps away from being beer). It's an essential part of the brewing process no matter what style you're making – and if you're brewing something especially hoppy, like an IPA, you'd use extra hops and tweak the timing of the boil.
But what if you want to turn the hop flavor up to 11, without adding too much extra bitterness? You dump a bunch of hops into your nearly-finished beer at the end of the brewing process and let it sit around for a while, absorbing all of the hoppy notes, then straining. It's called dry-hopping, and it extracts extra flavor from hops without making beer overly bitter since they're never heated.
Ester
A chemical compound that comes from yeast, often when the beer has been fermenting in warmer temperatures. They can impart a big range of flavors into a beer, depending on the specific type (they have chemistry textbook names like Isoamyl acetate or ethyl caprylate) and concentration, but generally provide a fruity or floral note. They're essential to styles like hefeweizen, which gets its signature banana flavor from intentional ester presence in the beer, but can be off-putting in other styles or in too high of a concentration, at which point they start to taste like solvent.
Gravity
A measure of beer's density that's important to brewing. Before fermentation, beer is basically just sugary water, at which point you measure the "original gravity." Once the yeast goes to town, that sugar is converted to alcohol and carbon dioxide, which very slightly lowers the liquid's density until a "final gravity" is reached. A consistent final gravity reading lets a brewer know that the yeast is done working, and by comparing the original and final readings, you can calculate the amount of alcohol in the beer.
Very alcoholic beers will have a higher original gravity reading – meaning the recipe used a lot of malt in order to get more fermentable sugars into the beer. That's why extra strong beers are sometimes referred to as "high gravity."
Haze
A cloudy appearance in lighter-colored beers. This has all kinds of different causes, like accidental infection from wild yeast or bacteria, temperature changes, or any number of brewing technicalities. With the exception of a few styles, haze is traditionally viewed negatively, with crystal-clear beer being the goal for most homebrewers and professionals. But some breweries have recently started to buck that trend with especially hoppy beers, where the hop oils are (supposedly) so overloaded that they create a hazy appearance. So it's mostly a matter of preference and style points, and can be (but isn't always) correlated with high hop flavor.
IBU
International bitterness units. A low IBU score from something like a light lager would be around 10, while a hopped-up IPA would be around 50 or higher. As a customer-facing measurement, though, it's largely unhelpful and used mostly as a marketing tool.
Some breweries like to tout the sky-high IBUs of their hoppy ales, but it's not a cut-and-dry measurement, since the bitterness needs to be considered relative to the beer's other ingredients. For example, a sweet and boozy barleywine might have 75 IBUs, but won't taste bitter because the hops are still low in relation to the extra high malt and alcohol presences.
And while the formula used to measure IBUs has no upper limit, there is a limit to the solubility of iso-alpha acids (hop resins) that maxes out around 110 IBU. So any hoppy beer claiming an IBU measurement over that number is likely pulling your leg.
Lupulin
A gland of the hop plant where all the deliciousness is hiding. Alpha and beta hop acids and essential hop oils reside here, and it's what imparts the delicious hoppy flavor into your favorite pale ales and IPAs.
Mash
As a verb, this is the first step in the brewing process where you soak malts in hot water. That releases sugars from the malts, which is later fermented to create beer. As a noun, this is the mixture of malts and hops from that step.
Mouthfeel
This is pretty self-explanatory – it's how the beer feels in your mouth. It's very similar to body, defined above, but also includes the physical interaction of the beer on your tongue. Is there an especially high amount of carbonation? Warming alcohol presence? It's quite technical and tough to notice unless you're really devoted to a tasting, but is considered one of the four components of evaluating a beer (along with aroma, appearance, and flavor) according to the Beer Judge Certification Program.
Phenol
Like esters, this is a chemical compound that imparts unique aromas (cloves, smoke, or medicine) and aroma to beer in certain concentrations. They can come from smoked malts, used in smoky styles like rauchbiers, certain fermenting techniques and yeast strains like brettanomyces, or chlorine that's present in the water used to brew.
The smoky, earthy, spicy notes can be great in moderation, but the more medicinal ones are harsh and undesirable.
Trappist
A Catholic order of monks and nuns who happen to be really, really good at brewing beer. The history stretches back to the Middle Ages, with the Trappist monasteries brewing beer both to serve their own communities and to sell for funding the monasteries' operations. There are only eleven monasteries in the world, most of which are in Belgium.
Usually, the beers are all bottle-conditioned Belgian ales – either dubbels, tripels, or quads.
Wet-Hopped
Most beers are brewed with hops that have been dried directly after harvest, in order to lengthen their shelf life so they're usable year-round. Once a year during the fall hop harvest, though, you can get fresh-off-the-vine "wet" hops, and brew with those. The fresh hops provide a more nuanced, earthy flavor to autumn brews. It's a subtle difference, and the resulting beers are only on shelves for a few weeks a year, but they're worth seeking out if you're an IPA fan.
Wort
The liquid that's created by the mash process. Basically, it's sugar water waiting to be hopped and then fermented into beer.
Once you've got a handle on all those, you'll be able to hold your own in most any beer conversation – and then some.
