In Italian, barista means bartender, and a traditional Italian barista runs the whole counter, serving espresso in the morning and cocktails, wine, and snacks in the evening. Italian plurals follow gender, baristi and bariste, while English and Spanish simply added an s and narrowed the job to espresso. That drink is demanding: water at about nine bars is forced through a dosed, distributed, and tamped puck in a window of roughly 25 to 30 seconds. Organic acids dissolve first, then sugars and lipids, then bitter tannins, so a shot pulled too fast tastes sour and one pulled too slow tastes astringent.

Milk has its own chemistry. Steam unfolds whey and casein proteins, which wrap around tiny air bubbles to form a stable microfoam, and clean latte art is visible proof it worked. A skilled barista also reads the farm: a dense Ethiopian bean grown near 2,000 meters may need a finer grind and hotter water than a softer Brazilian bean from 800 meters. Competitive barista culture began in Norway and grew into the World Barista Championship, won in 2009 by Gwilym Davies.

• Espresso comes from the Italian esprimere, to express.
• Tamping unevenly lets water channel down one side of the puck and ruins the shot.
• Too much air makes soapy bubbles, and overheating breaks the proteins so the milk tastes scorched.
• WBC competitors have 15 minutes to serve four espressos, four milk drinks, and four signature drinks to four sensory and two technical judges.
• The espresso and tonic spread from the competition stage to cafe menus across North America.