Spanakopita - Triangle (Τρίγωνο) is the handheld form of the spinach pie: a single-serving triangle folded from a strip of phyllo around the filling. Trígono means triangle, and the shape is the entire point. Where the pan-cut pie is a slice off a tray, this is a self-contained portion built to be picked up and eaten in the hand, off a bakery shelf or a street counter, which makes the fold and the seal matter as much as the filling.
The filling is the standard one, spinach pressed dry, feta, onion and dill, and the moisture discipline is unchanged because a wet filling in a small parcel soaks through fast and the whole thing goes limp in the hand. The folding is the distinct skill. A strip of oiled or buttered phyllo is laid out, a spoon of filling placed at one end, and the strip folded corner over corner down its length, the way a flag is folded, each turn wrapping the filling and sealing it inside successive layers. Done right, the last fold tucks under and the triangle bakes into a sealed, layered packet. Good execution is a triangle that crisps evenly on every face, holds its shape when lifted, flakes at the edges and keeps the filling moist and enclosed so it does not run down the wrist. Sloppy execution is a parcel folded loose or torn so the filling leaks and the corner bakes open, a pale soft pastry from skimped fat that bends instead of snapping, or a damp filling that turns the whole handheld soggy before it is even finished, the failure most punishing in a format that has to survive being eaten standing up.
The triangle is one of several shapes the same pie takes. The large pan-cut version sliced from a tray and the coiled rope wound into a spiral are distinct builds with their own geometry, and each deserves its own article rather than being crowded in here, as does the parent spinach pie. What the trígono contributes to the family is portability: the flag-fold that turns the pie into a single sealed handheld, governed by the same two rules as every form of it, a filling wrung dry and fat between every layer of phyllo.